Depending on the comment you may want to say something like, “I would love to talk about that after class”. Don’t make the student feel like they are in trouble as this can keep them from disclosing later on. Try to keep tabs on the student throughout the rest of the presentation. At the end of the presentation ask the child to join you where you can ask privately about the comment. Use open ended questions such as, “What did you mean by_____” or “Could you tell me more about _______”. Sometimes it will be nothing, other times it might be something, you never know so make sure to ask, just in case.