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: Rob traveled a distance of 30 km, covering the first 10 km in x minutes, the next 10 km in y minutes and the last 10 km in z minutes. If he totally took 3y minutes to cover the whole distance, then which of the following cannot be true? Assume x , y and z are different.

 Option A: z=3x

 Option B: x=3z

 Option C: y=2x

 Option D: x=2y

 Option E: y=3x
[EX A]: Option D

[EX Q]: Question: There are 3 questions in a question paper. If the questions have 4,3 and 2 solutions respectively, find the total number of solutions

 Option A: 24

 Option B: 25

 Option C: 30

 Option D: 40

 Option E: 54
[EX A]: Option A

[EX Q]: Question: Pumps A, B, and C operate at their respective constant rates. Pumps A and B, operating simultaneously, can fill a certain tank in 2 hours; pumps A and C, operating simultaneously, can fill the tank in 1 hours; and pumps B and C, operating simultaneously, can fill the tank in 2 hours. How many hours does it take pumps A, B, and C, operating simultaneously, to fill the tank.

 Option A: 1/3

 Option B: 1/2

 Option C: 1/4

 Option D: 5/2

 Option E: 5/6
[EX A]:
Option D