Active listening is best! I always try to repeat the questions my students ask me. This serves two purposes: one, it makes sure that I understood what the student was trying to understand (and sometimes it clarifies this for the student as well!); two, if there are other people present who might need to hear the question it ensures that they are able to hear and understand what is being asked.
Sometimes simply re-phrasing the question can help the student realize where they are going wrong or make the topic simply click and then they don't need an answer. If the student is the only one present I will try and get them to explain the situation/problem and solution to me to make sure they truly do understand the issue now. If others are present and that student says they do not need an explanation anymore I will usually say something along the lines of "Great! However, if others are having issues with this topic too I'd better go over the information just in case everyone hasn't made the connection yet."
