His colleagues could not tell me why did he not come to office yesterday. A. why not had he come B. why he did not come C. why had he not come D. No improvement

The correct answer is D. No improvement.

The sentence “His colleagues could not tell me why did he not come to office yesterday” is grammatically correct and conveys the intended meaning. The use of the past tense “did not come” is appropriate, as the speaker is referring to a specific event that happened in the past. The use of the interrogative pronoun “why” is also appropriate, as the speaker is asking for a reason or explanation.

The other options are all incorrect. Option A, “why not had he come,” is ungrammatical. The past participle “come” should be used after the auxiliary verb “had.” Option B, “why he

did not come,” is also ungrammatical. The subject and verb do not agree in number. Option C, “why had he not come,” is grammatically correct, but it is not the most natural way to express the sentence. The use of the past perfect tense “had not come” suggests that the speaker is asking about a reason or explanation for an event that happened before a specific time in the past. In this case, the speaker is simply asking why the person did not come to the office yesterday, so the simple past tense “did not come” is more appropriate.