You've asked a question and a student(s) has provided an answer. So now what? Most often the instructor simply returns to the lesson (lecture) and moves on. But good questioning involves drilling down from time to time to provide both more feedback to the instructor and making the student reflect more on their answer.
Here are a few suggestions or follow up comments and instructor can use once the student provides them the appropriate answer:
How did you arrive at that answer?
Can you explain why you believe that answer to be correct?
Can you provide an example to your answer?
What evidence do you have that supports your answer?
You can also get other students involved in the classroom during this process by asking some of the following questions:
Do you agree with the answer given by this student? Why or why not?
Can you arrive at a different answer or conclusion? Why or why not?
Can you add to the answer given?
Can you give us a different example?
Can you take us a different direction?