Which best proves why the expressions 4 (x + 3) + 2 x and 6 (x + 2) must be equivalent expressions?

A. When x = 3, both expressions have a value of 30.

B. When x = 5, both expressions have a value of 42.

C. When x = 1, both expressions have a value of 18, and when x = 8, both expressions have a value of 60.

D. When x = 2, both expressions have a value of 15, and when x = 6, both expressions have a value of 39.