The correct answer is C. to.
The word “to” is used to indicate the direction of an action. In this case, the action is “listening” and the direction is “to the question.” This is the most logical choice because it makes the most sense to listen to the question before answering it.
The other options are not as logical. The word “over” is used to indicate a position above or across something. In this case, it would not make sense to listen to the question “over” something. The word “for” is used to indicate a period of time. In this case, it would not make sense to listen to the question “for” a period of time. The word “at” is used to indicate a location or position. In this case, it would not make sense to listen to the question “at” something.
Therefore, the correct answer is C. to.