The correct answer is D.
“Beat about the bush” means to avoid the point or to speak in a roundabout way. In this case, the speaker is asking the listener to tell them plainly who broke the mirror, and not to try to avoid the question or to speak in a way that is difficult to understand.
Option A is incorrect because it suggests that the listener should put the blame on someone else. This is not what the speaker is asking for.
Option B is incorrect because it suggests that the listener should pretend to be unaware of the matter. This is also not what the speaker is asking for.
Option C is incorrect because it suggests that the listener should approach the matter in a round about way. This is also not what the speaker is asking for.