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: The number of diagonals of a polygon of n sides is given by the formula z=n(n-3)/2. If a polygon has twice as many diagonals as sides, how many sides does it have?

Option A: 3

Option B: 5

Option C: 6

Option D: 7

Option E: 8
[A]: Option B

[Q]: Question: A cycle is bought for Rs.900 and sold for Rs.1150, find the gain percent?

Option A: 15

Option B: 20

Option C: 27.77

Option D: 40

Option E: 12
[A]: Option C

[Q]: Question: The percentage increase in the area of a rectangle, if each of its sides is increased by 20% is:

Option A: 32%

Option B: 34%

Option C: 42%

Option D: 44%

Option E: 54%
[A]:
Option D