Consider the function ƒ(x) = (x + 1)2 – 1. Which of the following functions stretches ƒ(x) vertically by a factor of 4?

A) ƒ(x) = 1∕4(x + 1)2 – 4
B) ƒ(x) = (1∕4x + 1)2 + 3
C) ƒ(x) = 4(x + 1)2 – 1
D) ƒ(x) = 4(4x + 1)2 – 1