The correct answer is D. would have killed.
The sentence is in the past perfect conditional, which is used to talk about a hypothetical situation that did not happen. The past perfect tense is used to talk about an action that happened before another action in the past. The conditional tense is used to talk about a situation that is possible but not certain.
In this sentence, the bandits would have killed the man if the police had not reached there in time. This means that the bandits were planning to kill the man, but they were stopped by the police.
The other options are incorrect because they do not express the idea of a hypothetical situation that did not happen.
- Option A, did have killed, is in the past perfect tense. However, it is not used in a conditional sentence.
- Option B, will have killed, is in the future perfect tense. However, it is not used to talk about a hypothetical situation.
- Option C, would kill, is in the simple present tense. However, it is not used to talk about a hypothetical situation.
I hope this explanation is helpful. Please let me know if you have any other questions.