Which equation is an identity?
A.3(x – 1) = x + 2(x + 1) + 1
B.x – 4(x + 1) = –3(x + 1) + 1
C.2x + 3 = 1/2 (4x + 2) + 2
D.1.3(6x – 3) = 3(x + 1) – x – 2