Task: Question Answering
Input (English): Question: A can do a work in 15 days and B in 20 days. If they work on it together for 5 days, then the fraction of the work that is left is :

 Option A: 1/3

 Option B: 7/12

 Option C: 5/12

 Option D: 2/3

 Option E: 1/2
Output (English): Option C