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: A and B complete a work in 6 days. A can alone can do it in 10 days. If both can together can do the work in how many days?

 Option A: 7

 Option B: 3.75

 Option C: 2

 Option D: 1

 Option E: 8
[EX A]: Option B

[EX Q]: Question: (3x + 1) (2x - 5) = ax^2 + kx + n . What is the value of a - n + k ?

 Option A: 5

 Option B: 8

 Option C: 9

 Option D: 14

 Option E: 11
[EX A]: Option D

[EX Q]: Question: Four of the following five are alike in a certain way and hence form a group. Which one does not belong to the group?

 Option A: 70

 Option B: 80

 Option C: 52

 Option D: 48

 Option E: 68
[EX A]:
Option A