There are some students that just ask way too many questions! They love to have the attention. Most "questions" are not even questions at all. They are just comments that have nothing to do with the topic we are discussing.
One way I deal with this is by giving certain students post-its. The number depends on the students. It is usually around 5. Each time they ask a question/comment, they have to give a post-it. Once the post-its are done, they are done asking questions. They don't have to give the post-its when answering a question that I ask, only when they feel the need to interject something unrelated. It gets the children to really think about what they are saying. It also really eases the stress of that one child that needs too much attention for me.