Find the equation of tangent at $(x_1,y_1)$ for the parabola $y^2=4ax$?

Question

$\begin{array}{1 1}(a)\;2yy_1=2a(x+x_1)\\(b)\;yy_1=a(x+x_1)\\(c)\;yy_1=2a(x+x_1)\\(d)\;3yy_1=a(x+x_1)\end{array}$