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.

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
Option D

Question: If |x^2 − 20| = x, which of the following could be the value of x?

 Option A: -5

 Option B: -4

 Option C: 1

 Option D: 4

 Option E: 10
Option D

Question: The sequence x1, x2, x3,..., is such that Xn = 1/n - (1/(n+1)). What is the sum of the first 3 terms of the sequence?

 Option A: 201/100

 Option B: 99/100

 Option C: 100/101

 Option D: 1/10000

 Option E: 3/4

Option E