Ans: D
Consider the general case $y=a\cos(hx)+k$.
Consider the general case $y=a\cos(hx)+k$.
If $k$ is positive, then the graph translates upwards $k$ units. If $k$ is negative, then the graph translates downwards $-k$ units.
If $a > 1$, then the graph enlarges $a$ times along the $y$ axis. If $0 < a < 1$, the the graph enlarges $\dfrac{1}{a}$ times along the $y$ axis.
If $h > 1$, the the graph enlarges $\dfrac{1}{h}$ times along the $x$ axis. If $0 < h < 1$, the graph enlarges $h$ times along the $x$ axis.
Note that the graph of $y=\cos x^\circ$ is enlarged $3$ times along the $y$ axis and $\dfrac{1}{2}$ times along the $x$ axis, and then translated upwards $4$ units. Therefore, the equation of the graph is $y= 4+3\cos 2x^\circ$.
