Answer
The final answer is options (a) and (b)
Work Step by Step
The simple harmonic motion equation is given by
$$x(t)=x_{m} \cos (\omega t+\phi)$$
From figure 15-20a, the displacement $x_o$ is negative at time $t=0$, so at $t=0$, $\cos \phi$ must be negative.
For option (a), we have $-\pi
