The ratio of the magnitudes of maximum acceleration to the corresponding velocity of a body undergoing simple harmonic motion, $x=a\sin 2\pi ft$ is

In case of a simple harmonic motion, if the velocity is plotted along the $X$ -axis and the displacement (from the equilibrium position) is plotted along the $Y$ -axis, the resultant curve happens to be an ellipse with the ratio:
$\frac{\text{ major axis }\left(\text{along }X\right)}{\text{ minor axis }\left(\text{along }Y\right)}=20\pi$

What is the frequency of the simple harmonic motion?

The displacement time graph of a particle executing SHM is given in figure: (sketch is schematic and not to scale) 

Which of the following statements is/are true for this motion? 

(A) The force is zero at $t=\frac{3T}{4}$
(B) The magnitude of acceleration is maximum at $t=T$
(C) The speed is maximum at $t=\frac{T}{4}$
(D) The $P.E.$ is equal to $K.E.$ of the oscillation at $t=\frac{T}{2}$