The length of the chord of the parabola \(y^{2}=4 a x(a>0)\) which passes through the vertex and makes an acute angle \(\alpha\) with the axis of the parabola is
(A) \(\pm 4 \mathrm{a} \cot \alpha \operatorname{cosec} \alpha\)
(B) \(4 \mathrm{a} \cot \alpha \operatorname{cosec} \alpha\)
\(\begin{array}{ll}\text
{ (C) }-4 \mathrm{a} \cot \alpha \operatorname{cosec} \alpha & \text
{ (D) } 4 \mathrm{a} \operatorname{cosec}^{2} \alpha\end{array}\)
