Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.

[EX Q]: Problem: it is only in the second option we find the sentence a in continuation with the opening sentence d. sentence a alone explains, why the fear has such enormous effect on the human beings.
Options: a. 28, b. 99, c. 728, d. 27, e. 271
[EX A]: b

[EX Q]: Problem: what is the rate percent when the simple interest on rs. 810 amount to rs. 155 in 4 years ?
Options: a. 4.78, b. 4.68, c. 4.58, d. 4.48, e. 4.38
[EX A]: a

[EX Q]: Problem: a semicircular shaped window has diameter of 63 cm. its perimeter equals
Options: ['a. 162', 'b. 766', 'c. 298', 'd. 277', 'e. 198']
[EX A]:
a