For an real number k, which of the following must be a real number?

A)1/k

B)k/k+1

C)1/k-1

D) k/k^2+1

E) 1/k^2-1Thank you

If it’s possible to make the denominator equal zero, then you can eliminate the choice. (A) is not real when *k* = 0. (B) is not real when *k* = -1. (C) is not real when *k* = 1. (E) is not real when *k* = 1 or -1.

(D) is the answer because there’s no value of *k* that makes equal zero.