Task: Question Answering
Input (English): Question: In a group of 20 students, each student is registered for at least one of three classes – History, Math and English. 10 students are registered for History, 10 students are registered for Math, and 15 students are registered for English. If only three students are registered for all three classes, how many students are registered for exactly two classes?

 Option A: 13

 Option B: 10

 Option C: 9

 Option D: 8

 Option E: 7
Output (English): Option C