The length of the latus-rectum of the parabola whose focus is \[\left( \frac{{{u}^{2}}}{2g}\sin 2\alpha ,\ -\frac{{{u}^{2}}}{2g}\cos 2\alpha \right)\] and directrix is \[y=\frac{{{u}^{2}}}{2g}\], is

• A.            \[\frac{{{u}^{2}}}{g}{{\cos }^{2}}\alpha \]                                   
• B.            \[\frac{{{u}^{2}}}{g}\cos 2\alpha \]
• C.            \[\frac{2{{u}^{2}}}{g}{{\cos }^{2}}2\alpha \]                               
• D.            \[\frac{2{{u}^{2}}}{g}{{\cos }^{2}}\alpha \]