The locus of the mid point of the line segment joining the focus to a moving point on parabola $y^2=4ax$ is another parabola with direction

Question

$\begin{array}{1 1}(A)\;x=-a \\(B)\;x=\large\frac{-a}{2} \\(C)\;x=0 \\(D)\;x=\large\frac{a}{2} \end{array}$