If $(1+i)(1+2i)(1+3i).....(1+ni)=x+iy$, then $2.5.10.....(1+n^2)$ = ?

Question

$\begin{array}{1 1}(A) \; x^2+y^2 \\(B)\;x^2-y^2 \\(C)\;(x+iy)^2 \\(D)\; (x-iy)^2 \end{array}$