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: On dividing 21 by a number, the quotient is 10 and the remainder is 1. Find the divisor.

 Option A: 1

 Option B: 2

 Option C: 4

 Option D: 6

 Option E: 7

Option B