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: If integers a and b are distinct factors of 30, which of the following CANNOT be a factor of 30?
I. ab + b^2
II. (a + b)^2
III. a + b

 Option A: I only

 Option B: II only

 Option C: III only

 Option D: I and II only

 Option E: I, II, and III
Option B

Question: A certain sum earns simple interest of Rs. 800 in 2 years at a certain rate of interest. If the same sum earns compound interest of Rs.900in the same period of 2 years, What must be the rate of interest?

 Option A: 25%

 Option B: 10%

 Option C: 15%

 Option D: 20%

 Option E: 30%
Option A

Question: Two trains, A and B, started simultaneously from opposite ends of a 75-mile route and traveled toward each other on parallel tracks. Train A, traveling at a constant rate, completed the 75-mile trip in 3 hours; Train B, traveling at a constant rate, completed the 75-mile trip in 2 hours. How many miles had train A traveled when it met train B?

 Option A:  20

 Option B:  22.5

 Option C:  30

 Option D:  37.5

 Option E:  45

Option C