I don't know how to ask a question about why there are so many people in a place.
For ex: You are student of a university. Normally, each class of your university only has 20 students. However, today, when you go to your class, there are about 30 students. You want to ask your friend sitting next to you that why there are so many students here. How will I ask?
Why are so many students in the class today?
Is it correct?