P is a point, two tangents are drawn from it to the parabola $y^2=4x$ such that the slope of one tangent is three times the slope of the other. The locus of P is

Question

$\begin{array}{1 1}(A)\;\text{a straight line} \\(B)\;\text{a circle} \\(C)\;\text{a parapola} \\(D)\;\text{an ellipse} \end{array}$