Task: Question Answering
Input (English): Question: Two pipes A and B together can fill a cistern in 4 hours. Had they been opened separately, then B would have taken 6 hours more than A to fill cistern. How much time will be taken by A to fill the cistern separately?

 Option A: 3

 Option B: 5

 Option C: 6

 Option D: 8

 Option E: 9
Output (English): Option C