Answer:
B. 4
Explanation:
We have the equation x^2 = 16 and we want to solve for x.
Square root both sides:

x = +/- 4
A rational expression is considered undefined when the denominator is equal to 0 (in other words, we get something like k/0, which is undefined). Here, the because
when x = 4, then the answer is B.
Hope this helps!