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.

Correct option is B

The segment that contains a grammatical error in the sentence is "(b) I read."
 The correct form should be "I was reading" to convey the continuous action of reading at the time of falling asleep. The sentence should read, "I fell asleep while I was reading the book."
 The use of the past continuous tense ("was reading") is appropriate here to indicate an ongoing action (reading) that was interrupted by another action (falling asleep).
 The other segments "(a) the book," "(c) asleep while," and "(d) I fell" are grammatically correct.
 Therefore, the segment with the error is (b) "I read."

Grammatical Rule: When talking about an action that was ongoing at a specific time in the past and was interrupted by another action, we use the past continuous tense.

Example:

• I was watching TV when the phone rang.
• This illustrates the use of the past continuous tense ("was watching") to indicate an action occurring at the same time as another action in the past.