Periodic Motion & SHM Basics question from NEET 2019

Answer: (c)

1. $r = 3\ \text{m}$, $T = 4\ \text{s}$, so $\omega = \frac{2\pi}{4} = \frac{\pi}{2}\ \text{rad/s}$.
2. At $t = 0$, P is on the $+y$ axis, so $y(0) = +3\ \text{m}$ (maximum); it moves clockwise, so $y$ decreases.
3. Hence $y(t) = 3\cos\left(\frac{\pi t}{2}\right)$ m.
4. So the answer is (c).