Which is not a polynomial identity?

A.
(m − n)2 = m2 − 2mn + n2

B.
3(x − 6)2 = 3x2 − 18x + 108

C.
x4 − 24 = (x + 2)(x3 − 2x2 + 4x − 8)

D.
4(3x − 1)(x + 6) = 12x2 + 68x − 24