CDS English · Spotting Errors
Verb forms: the right shape after every helper
Once the tense is right, check the shape of the verb: the correct past form, the plain form after a modal, be + past participle in the passive, and -ing or to + verb where each belongs.
Why this matters
These errors sit in one word: 'have ran' for 'have run', 'to described' for 'to describe', 'was been resolved' for 'was resolved'. Each helper word demands one form of the verb after it. Learn what has, did, can, must, to and worth demand, and these items take seconds.
Concept 1 of 5: Irregular verbs: past and past participle
Every verb has three main forms. Regular verbs add -ed for the second and third forms (walk, walked, walked). Irregular verbs change in their own way (go, went, gone), and the exam picks the ones students get wrong.
Definition
- V1, the base form: the dictionary form (go, run, spring).
- V2, the simple past: used alone, with no helper: 'He ran home.'
- V3, the past participle: used after has/have/had, and after a form of be in the passive: 'He has run', 'The floor was swept'.
- The check: after has/have/had, use V3. In a past sentence with no helper, use V2.
- Hang has two sets of forms: hang, hung, hung for objects (a picture, a shirt); hang, hanged, hanged only for putting a person to death.
| Base (V1) | Past (V2) | Past participle (V3) | Tested in |
|---|---|---|---|
| sweep | swept | swept | 2017 (I)Q |
| run | ran | run | 2019 (II)Q |
| spring (jump up) | sprang | sprung | 2025 (I)Q |
| hang (an object) | hung | hung | 2025 (I)Q 'Hanged' is only for putting a person to death. A shirt or a picture is hung. |
Also learn: begin, began, begun; drink, drank, drunk; swim, swam, swum; ring, rang, rung; lie, lay, lain; lay, laid, laid; seek, sought, sought.
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
CDS · 2017 · CDS (I) 2017 — English · Q43Easy
Example 1 · Spotting Errors · Verb Forms and Voice
Directions: find error in underlined part or No error
The peon has not sweeped the floor today.
V2 after 'has' or 'have'
'Have ran', 'has began', 'had drank' all use the simple past where the past participle is needed. After has/have/had, always check that the verb is the third form.
Adding -ed to an irregular verb
'Catched', 'teached', 'bringed' do not exist. When a familiar verb ends in -ed in the sentence, stop and check whether it is irregular: caught, taught, brought.
'Sprung' is not the past
'She sprung up from her bed' uses V3 with no helper. The simple past is 'sprang'. The same pattern catches 'sung' for 'sang' and 'begun' for 'began'.
Concept 2 of 5: Base form after do/did, modals and 'to'
Some helpers must be followed by the plain base form of the verb and nothing else: no -s, no -ed, no -ing. Spot the helper, then check the very next verb.
Definition
- After do / does / did: base form. 'Did he reach?' 'She does not know.' The helper already carries the tense and the -s.
- After a modal (can, could, may, might, shall, should, will, would, must): base form. 'She can swim', not 'can swims'.
- After to when it is part of the verb (to + verb): base form. 'too tired to walk', 'went there to improve'.
- After appear, seem, want, hope, try: to + base form. 'They appear to like the place.'
- Careful: in 'look forward to', 'be used to' (be accustomed to) and 'with a view to', the word 'to' is a preposition and takes a noun or -ing: 'I look forward to meeting you.'
Worked example
Find the part with the error. (a) The old man (b) did not wanted (c) to sell his land. (d) No error
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
CDS · 2020 · CDS (II) 2020 — English · Q15Moderate
Example 2 · Spotting Errors · Verb Forms and Voice
Directions: find the part with an error, or no error
The greatest merit of democracy is that everyone feels free and can pursues his/her interest.
The helper takes the ending, not the main verb
'Did reached', 'does knows' and 'can goes' mark the tense or the -s twice. Only the helper changes; the main verb stays plain.
'No sooner' still uses did + base form
After 'No sooner', the helper comes before the subject: 'No sooner did I reach there than the children left.' The verb after 'did' stays in the base form, and the pair is 'no sooner ... than'.
Not every 'to' takes the base form
In 'look forward to', 'object to', 'be used to' and 'lead to', 'to' is a preposition. It takes a noun or an -ing form: 'I look forward to hearing from you', not 'to hear'.
Concept 3 of 5: Passive voice: be + past participle, and when not to use it
In the active voice the subject does the action: 'The clerk sent the letter.' In the passive voice the subject receives it: 'The letter was sent.' The passive always needs two parts: a form of be and the past participle.
Definition
- Passive = be + past participle (V3): is sent, was sent, has been sent, will be sent, should be sent, to be sent.
- Both parts must be there. 'Things are achieve' lacks the V3 ('are achieved'). 'These shoes designed for runners' lacks the be ('are designed').
- There is no 'was been'. The past passive is was + V3 ('was resolved'); the perfect passive is has/had been + V3 ('has been resolved').
- A verb that has its own object stays active: 'Wind power has made steady progress' ('progress' is the object, so no 'been').
- An adjective after the subject takes a form of be, not have: 'He is unwilling', 'She is aware'.
- After a modal: modal + be + V3 ('should be done'). After to: to be + V3 ('to be updated').
Worked example
Find the part with the error. (a) The results (b) were announce (c) on Monday. (d) No error
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
CDS · 2023 · CDS (II) 2023 — English · Q45Moderate
Example 3 · Spotting Errors · Verb Forms and Voice
Directions: find error in three underlined parts or No error
If you are interested in applying for the job, your application must received by Friday.
A passive needs both parts
Check for a form of be AND a past participle. Drop either one and the verb is broken: 'are achieve', 'shoes designed for runners'.
'Was been' is never right
'Been' needs has, have or had before it. 'The matter was been resolved' should be 'was resolved' or 'has been resolved'.
Don't make an active verb passive
If the verb has its own object, the subject is doing the action: 'Wind power has made steady progress', not 'has been made steady progress'.
'Has' before an adjective
Unwilling, afraid, aware and able are adjectives. They take 'is' or 'was': 'he is unwilling to move', not 'he has unwilling'.
Concept 4 of 5: Gerund, infinitive, participle: worth doing, parallel lists, dangling participles
Some verb forms show no tense: the -ing form, to + verb, and the past participle. Certain words decide which of these must follow them. A list must keep one form all through. And an opening -ing phrase must belong to the subject that follows it.
Definition
- Gerund: the -ing form used as a noun: 'Swimming is fun.'
- Infinitive: to + base form: 'to swim'.
- Participle: the -ing or V3 form used like an adjective: 'a running tap', 'a broken chair'.
- After worth, busy, no use, and after any preposition (about, for, of, in, at, without, before), use the -ing form.
- Parallelism: items in a list or a pair take the same form: 'to take, to mail and to call', or 'taking, mailing and calling'.
- A dangling participle is an opening -ing phrase with no proper doer in the main clause. 'Walking down the road, the trees looked lovely' says the trees were walking. The subject after the comma must be the one doing the -ing.
| Word or pattern | What follows | Correct example | Tested in |
|---|---|---|---|
| worth | -ing form | This book is worth reading twice. | 2017 (I)Q |
| anxious about (a preposition) | -ing form | She was nervous about having to speak first. | 2018 (I)Q |
| lead to ('to' is a preposition) | a noun or -ing form | Hard work can lead to success. | 2019 (I)Q |
| a list of duties | one form all through | His duties are to take notes, to answer calls and to file letters. | 2017 (II)Q |
| an opening participle phrase | the subject that does the action | It being a rainy day, we stayed indoors. | 2017 (I)Q |
Other words that take -ing: avoid, enjoy, finish, mind, can't help, insist on, succeed in, interested in.
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
CDS · 2017 · CDS (I) 2017 — English · Q26Moderate
Example 4 · Spotting Errors · Verb Forms and Voice
Directions: find error in underlined part or No error
If a thing is worth doing at all it is worth done well.
'To' is sometimes a preposition
In 'lead to', 'look forward to', 'object to' and 'be used to', the 'to' takes a noun or -ing form. 'This will lead to escape suffering' is wrong; 'lead to escaping suffering' or 'lead to escape from suffering' is right.
A list breaks at the point where the form changes
In 'to take the minutes, mailing the letters and calling the members', the first item does not match the other two. Mark the part where the forms mix.
Dangling opener: ask who is doing it
'Being a rainy day, we did not go out' says that we were a rainy day. Fix it with its own subject: 'It being a rainy day' or 'As it was a rainy day'.
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Reference tables (2)
Irregular verbs: past and past participle4 rows
| Base (V1) | Past (V2) | Past participle (V3) | Tested in |
|---|---|---|---|
| sweep | swept | swept | 2017 (I)Q |
| run | ran | run | 2019 (II)Q |
| spring (jump up) | sprang | sprung | 2025 (I)Q |
| hang (an object) | hung | hung | 2025 (I)Q 'Hanged' is only for putting a person to death. A shirt or a picture is hung. |
Also learn: begin, began, begun; drink, drank, drunk; swim, swam, swum; ring, rang, rung; lie, lay, lain; lay, laid, laid; seek, sought, sought.
Gerund, infinitive, participle: worth doing, parallel lists, dangling participles5 rows
| Word or pattern | What follows | Correct example | Tested in |
|---|---|---|---|
| worth | -ing form | This book is worth reading twice. | 2017 (I)Q |
| anxious about (a preposition) | -ing form | She was nervous about having to speak first. | 2018 (I)Q |
| lead to ('to' is a preposition) | a noun or -ing form | Hard work can lead to success. | 2019 (I)Q |
| a list of duties | one form all through | His duties are to take notes, to answer calls and to file letters. | 2017 (II)Q |
| an opening participle phrase | the subject that does the action | It being a rainy day, we stayed indoors. | 2017 (I)Q |
Other words that take -ing: avoid, enjoy, finish, mind, can't help, insist on, succeed in, interested in.
Watch out for (16)
- V2 after 'has' or 'have'→ Irregular verbs: past and past participle
- Adding -ed to an irregular verb→ Irregular verbs: past and past participle
- 'Sprung' is not the past→ Irregular verbs: past and past participle
- The helper takes the ending, not the main verb→ Base form after do/did, modals and 'to'
- 'No sooner' still uses did + base form→ Base form after do/did, modals and 'to'
- Not every 'to' takes the base form→ Base form after do/did, modals and 'to'
- A passive needs both parts→ Passive voice: be + past participle, and when not to use it
- 'Was been' is never right→ Passive voice: be + past participle, and when not to use it
- Don't make an active verb passive→ Passive voice: be + past participle, and when not to use it
- 'Has' before an adjective→ Passive voice: be + past participle, and when not to use it
- 'To' is sometimes a preposition→ Gerund, infinitive, participle: worth doing, parallel lists, dangling participles
- A list breaks at the point where the form changes→ Gerund, infinitive, participle: worth doing, parallel lists, dangling participles
- Dangling opener: ask who is doing it→ Gerund, infinitive, participle: worth doing, parallel lists, dangling participles
- 'Isn't it?' is not a tag for every sentence→ Word order in questions, reported questions and question tags
- Reported questions do not invert→ Word order in questions, reported questions and question tags
- The tag takes the opposite sign→ Word order in questions, reported questions and question tags
Test yourself on Spotting Errors
25 past CDS questions from this chapter, timed at 25 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.