Past continuous for the action in progress when another happened

This type of question, asked 3 times: 18 Jul 2023 S2, 24 Sep 2024 S3, 23 Sep 2025 S1. All 3 questions below, oldest first.

Try each one first, then open its answer.

Question 1
18 Jul 2023 S2
80 $The following sentence has been split into four segments. Identify the segment that contains a grammatical error. I fell / asleep while / I read / the book.$
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Question 2
24 Sep 2024 S3
95 $The given sentence is divided into four segments. Select the option that has the segment with a grammatical error. Jerry driving / home late / when the incident / took place.$
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Question 3
23 Sep 2025 S1
95 $Choose the most suitable option to replace the highlighted part of the sentence: He *is sleeping when I called * him.$
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Question 1