Factorize : $a^2+2ab+b^2-c^2-2cd -d^2$

Question

$\begin{array}{1 1} (a+b)^2 \\ (a+b)^2(c+d)^2 \\ (a+b+c+d)^2 \\ (a+b)^2-(c+d)^2 \end{array} $