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.

[Q]: Question: A man can do a piece of work in 5 days, but with the help of his son he can do it in 3 days. In what time can the son do it alone ?

 Option A: 13/2

 Option B: 19/2

 Option C: 21/2

 Option D: 15/2

 Option E: None
[A]: Option C


[Q]: Question: Two stations A and B are 20 km apart on a straight line. One train starts from A at 7 a.m. and travels towards B at 20 kmph. Another train starts from B at 8 a.m. and travels towards A at a speed of 25 kmph. At what time will they meet?

 Option A: 9

 Option B: 10

 Option C: 11

 Option D: 12

 Option E: 8
[A]: Option E


[Q]: Question: A set of data consists of the following 4 numbers: 0, 2, 4, 6, and 8. Which two numbers, if added to create a set of 7 numbers, will result in a new standard deviation that is close to the standard deviation for the original 5 numbers?

 Option A: -1 and 9

 Option B: 4 and 4

 Option C: 3 and 5

 Option D: 2 and 6

 Option E: 0 and 8
[A]:
Option E