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: The greatest common factor of 16 and the positive integer n is 4, and the greatest common factor of n and 45 is 3. Which of the following could be the greatest common factor of n and 210?

 Option A: 3

 Option B: 14

 Option C: 30

 Option D: 42

 Option E: 70
[EX A]: Option D

[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: A train of 35 carriages, each of 60 meters length, when an engine also of 60 meters length is running at a speed of 60 kmph. In what time will the train cross a bridge 1.5 km long?

 Option A: 6

 Option B: 3

 Option C: 4

 Option D: 9

 Option E: 3.6
[EX A]:
Option E