Find the value of $(a^2+\sqrt{a^2-1})^4+(a^2-\sqrt{a^2-1})^4$

Question

$\begin{array}{1 1}(A)\;2(a^8+6a^6-5a^4-2a^2+1)\\(B)\;4\\(C)\;(a^8+6a^6-5a^4-2a^2+1)\\(D)\;a^5+6a^4-5a^3-2a+1\end{array} $