#### Answer

D

#### Work Step by Step

In the standard equation $y=-a \cos bx$, $a$ is the amplitude while $b$ can be used to find the period. In the equation $y=-3 \cos \frac{1}{2}x$, $a=3$ while $b=\frac{1}{2}$.
Since $a=3$, this means that the amplitude is 3.
Now we use $b$ to find the period using the formula:
Step 1: Period$=\frac{2\pi}{b}$
Step 2: Period$=\frac{2\pi}{1/2}$
Step 3: Period$=2\pi \times 2$
Step 4: Period$=4\pi$
Therefore, we know that the amplitude is 3 while the period is $4\pi$. This means that Option D is the one among all the options that is false.