The trajectory of a projectile in a vertical plane is $y =\alpha x -\beta x ^{2},$ where $\alpha$ and $\beta$ are constants and $x \& y$ are respectively the horizontal and vertical distances of the projectile from the point of projection. The angle of projection $\theta$ and the maximum height attained $H$ are respectively given by :-

• A

  $\tan ^{-1} \alpha, \frac{\alpha^{2}}{4 \beta}$

• B

  $\tan ^{-1} \beta, \frac{\alpha^{2}}{2 \beta}$

• C

  $\tan ^{-1} \alpha, \frac{4 \alpha^{2}}{\beta}$

• D

  $\tan ^{-1}\left(\frac{\beta}{\alpha}\right), \frac{\alpha^{2}}{\beta}$