CDS English · Spotting Errors
Sentence improvement: test each option in the sentence
A sentence with one part underlined and three possible replacements: put each option into the sentence, read it whole, and keep the original (No improvement) when it is already right.
Why this matters
Sentence improvement was a full section of the 2017 (I) paper and came back in 2024 (II). The rules it tests are the same as in spotting errors: tense, agreement, prepositions and word choice. What is new is the format. You must judge three replacements as well as the original, and 'No improvement' is a real answer, not a last resort.
Concept 1 of 2: When the underlined part is already right
Definition
The method:
- Read the whole sentence first, with the underlined part as printed. Run the usual checks: time marker, agreement, preposition, word choice.
- If the original passes every check, it is a candidate for No improvement.
- Now put each option into the sentence and read the whole sentence again. An option must fit the words around it, not just make sense alone.
- Reject an option that is wrong, awkward, or only a synonym with no gain ('occurring' for 'happening').
- Choose No improvement when the original is correct and no option is clearly better.
Worked example
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
Example 1 · Spotting Errors · Sentence Improvement
A synonym is not an improvement
Read the option inside the sentence
Look-alike forms are the usual decoys
Check the words outside the underline
Concept 2 of 2: Improving the verb: tense and agreement
Definition
Tense rules the 2017 (I) paper tested:
- After till, until, when, before, after, if, use the present for a future action, not 'will': 'Wait till I come back.'
- By + a past time → past perfect: 'By noon he had finished.'
- The earlier of two past actions takes the past perfect when the order matters: 'He disappeared after he had rescued the boy.'
- A finished period in the past ('for ten years when I was a child') takes the simple past: 'I lived there for ten years.'
- Third conditional (an unreal past): 'If he had come, he would have seen it.' But for = 'if it had not been for', and takes the same result: 'But for the rain, we would have won.'
- A stative verb describes a state, not an action: exist, know, belong, own, contain, seem. It is not used in the -ing form: 'does not exist'.
Agreement: 'along with', 'together with', 'with' and 'as well as' do not add to the subject. 'The teacher, along with her children, was ...'.
Worked example
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
Example 2 · Spotting Errors · Sentence Improvement
No 'will' after till, when or before
'Ought to have' is not a conditional result
Stative verbs reject the -ing form
'Along with' does not make a plural
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.
Watch out for (8)
- A synonym is not an improvement→ When the underlined part is already right
- Read the option inside the sentence→ When the underlined part is already right
- Look-alike forms are the usual decoys→ When the underlined part is already right
- Check the words outside the underline→ When the underlined part is already right
- No 'will' after till, when or before→ Improving the verb: tense and agreement
- 'Ought to have' is not a conditional result→ Improving the verb: tense and agreement
- Stative verbs reject the -ing form→ Improving the verb: tense and agreement
- 'Along with' does not make a plural→ Improving the verb: tense and agreement
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.