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: If x and y are negative integers, which of the following statements must be true?
I. (-x)^y is positive.
II. (-x)^(-y) is positive.
III. x^(-y) is positive.

 Option A: None

 Option B: II only

 Option C: I and II

 Option D: I and III

 Option E: I, II and III
[A]: Option C


[Q]: Question: The average salary per head of the entire staff of an office including the officers and clerks is Rs.90. The average salary of officers is Rs.500 and that of the clerks is Rs.84. If the number of officers is 2, find the number of officers in the office?

 Option A: 620

 Option B: 720

 Option C: 820

 Option D: 920

 Option E: 1020
[A]: Option C


[Q]: Question: what is average of 2000 terms of the given series
1,-3,2,-4,3,-5,4,....

 Option A: 1

 Option B: 0.5

 Option C: -0.5

 Option D: -1

 Option E: -2
[A]:
Option D