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.

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

Question: A box contains 9 pairs of shoes (18 shoes in total). If two shoes are selected at random, what it is the probability that they are matching shoes?

 Option A: 1/190

 Option B: 1/17

 Option C: 1/19

 Option D: 1/10

 Option E: 1/9
Option B

Question: The compound interest earned on a sum for the second and the third years are $1400 and $1498 respectively. What is the rate of interest?

 Option A: 3%

 Option B: 5%

 Option C: 7%

 Option D: 9%

 Option E: 11%

Option C