The derivative of a function f is given by f'(x) = x^3 - 4 sin(x^20 + 1. On the interval (-2.5, 2.5), at which of the following values of x dos f have a relative maximum?
A. -1.970 and 0
B. -1.467 and 1.075
C. -0.475, 0.542, and 1.396
D. -0.475 and 1.396 only
E. 0.542 only