There are two examinations rooms A and B. If 10 students are sent from A to B, then the number of students in each room is the same. If 20 candidates are sent from B to A, then the number of students in A is double the number of students in B. The number of students in room A is:

1. A Option A: 20
2. B Option B: 80
3. C Option C: 100
4. D Option D: 200

How we write and check questions