The correct answer is D. By whom is this mess being created?
The other options are incorrect because they use the past tense, which is not appropriate for a question about an ongoing event. The past tense is used to talk about events that have already happened, while the present tense is used to talk about events that are happening now or that happen regularly.
In this case, the question is asking who is creating the mess, which is an ongoing event. Therefore, the correct answer should use the present tense.
The other options also have other problems. Option A, Who has been created this mess?, is grammatically incorrect. The correct verb form is “created,” not “been created.” Option B, By whom has this mess been created?, is also grammatically incorrect. The correct preposition is “by,” not “has.” Option C, By whom this mess is being created?, is grammatically correct, but it is not the most natural way to ask the question. The most natural way to ask the question is to use the pronoun “who,” as in Option D.
Therefore, the correct answer is D. By whom is this mess being created?