Which could be the first step of an indirect proof of the conditional below? Select all that apply.
If x = 4, then 4x = x2.
A. If 4x ≠ x2, then x ≠ 4.
B. If x = 4, then 4x = x2.
C. Assume if 4x ≠ x2, then x ≠ 4.
D. Assume if x ≠ 4, then 4x ≠ x2.