Definition: You are given a math word problem and you are supposed to make use of mathematical concepts like probability, combinatorics, linear equations, sequences/series, or simple operators like addition, subtraction, division, or multiplication to answer the given question. Choose the best option from the 5 given options and report that option.
Input: Question: A is twice as fast as B. If B alone can do a piece of work in 10 days, in what time can A and B together complete the work?

 Option A: 10/3

 Option B: 8

 Option C: 9

 Option D: 7/3

 Option E: 12

Option A