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.

[EX Q]: Question: In a box, there are 8 red, 7 blue and 6 green balls. One ball is picked up randomly. What is the probability that it is neither red nor green?

 Option A: 1/3

 Option B: 2/5

 Option C: 3/7

 Option D: 8/27

 Option E: 9/29
[EX A]: Option A

[EX Q]: Question: A seller of used cars has 18 cars to sell and each of his clients selected 3 cars that he liked most. If each car was selected exactly thrice, how many clients visited the garage?

 Option A: 8

 Option B: 10

 Option C: 12

 Option D: 18

 Option E: 16
[EX A]: Option D

[EX Q]: Question: In how many ways can five different rings be worn on four fingers of one hand?

 Option A: 10

 Option B: 5

 Option C: 15

 Option D: 16

 Option E: 18
[EX A]:
Option B