Ans: D
Refer to the graph of $y=\cos x^\circ$, the given graph in the figure is reflected along the $x$-axis and then translated to the right $60^\circ$.
Refer to the graph of $y=\cos x^\circ$, the given graph in the figure is reflected along the $x$-axis and then translated to the right $60^\circ$.
Therefore, the function of the given graph is $y=-4\cos (x^\circ -60^\circ)$.
Hence, $a=-4$ and $\theta = -60^\circ$.
