Which expression is equivalent to 8x^3 − 64 when factored completely?

a
(2x − 4)(4x^2 + 8x + 16)

b
(2x − 4)(4x^2 − 8x + 16)

c
(2x + 4)(4x^2 + 8x + 16)

d
(2x + 4)(4x^2 + 8x − 16)