Which of the following is a true polynomial identity?
a) a^6+b^6 = (a^2 + b^2)(a^4 + a^2b^2 + b^4)
b) a^6 - b^6 = (a^2+b^2)(a²-ab+b²)(a²+ab + b²)
c) a^6 - b^6 = (a³-b³)(a-ab+b)(a²+ab+b²)
d) a^6 - b^6 = (a²-b²)(a²-ab+b^2)(a^2+ab+b^2)​