Answer
D
Work Step by Step
Comparing $y=\sin 3x$ with the standard form of the sin function $y=a\sin bx$, we find that $a=1$ while $b=3$. This means that the amplitude is 1 while the period is $\frac{2\pi}{b}=\frac{2\pi}{3}$.
Therefore, we need to find a sin graph whose amplitude is 1 and whose period is $\frac{2\pi}{3}$. Such a graph is found in option D.