$\begin{aligned} \therefore \quad \frac{\mathrm{k}}{\mathrm{U}}= \frac{\mathrm{v}^{2}}{\omega^{2} \mathrm{x}^{2}}=\left(\frac{\cos (\mathrm{wt})}{\sin (\mathrm{wt})}\right)^{2} \\ =\cot ^{2}\left(\frac{\pi}{90} \times 210\right) \\= \cot ^{2}\left(2 \pi+\frac{\pi}{3}\right) \\=\left(\frac{1}{\sqrt{3}}\right)^{2}=\frac{1}{3} \end{aligned}$


$(A)$ Restoring force is directly proportional to the displacement.
$(B)$ The acceleration and displacement are opposite in direction.
$(C)$ The velocity is maximum at mean position.
$(D)$ The acceleration is minimum at extreme points.
Choose the correct answer from the options given below :