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 man’s speed with the current is 18 km/hr and the speed of the current is 2.5 km/hr. the man’s speed against the current is :

 Option A: 8.5 km/hr

 Option B: 9.5 km/hr

 Option C: 13 km/hr

 Option D: 12.5 km/hr

 Option E: None of these

Option C