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: If the operation ∆ is defined by a ∆ b = (b - a)^2/a^2 for all numbers a and b, and a ≠ 0, then what is the result when we evaluate this expression: (-5) ∆ (5 ∆ −5) ?

 Option A: 49/9

 Option B: 49/16

 Option C: 81/16

 Option D: 81/25

 Option E: 100/81
[EX A]: Option D

[EX Q]: Question: There r 4 prime numbers in ascending order. The multiplication of first 3 is 385 and that of last 3is 1001. what is the last number is

 Option A: 12

 Option B: 15

 Option C: 16

 Option D: 13

 Option E: 18
[EX A]: Option D

[EX Q]: Question: 54671 - 18456 - 33466 = ?

 Option A: 2749

 Option B: 5449

 Option C: 6749

 Option D: 6449

 Option E: 6468
[EX A]:
Option A