1. The graph of the function $y=2 \sin \left(3 x-\frac{\pi}{2}\right)$ is shifted to the left by $\varphi(\varphi>0)$ units, and the resulting graph corresponds to an odd function. Then the minimum value of $\varphi$ is ( ).
(A) $\frac{\pi}{3}$
(B) $\frac{\pi}{4}$
(C) $\frac{\pi}{6}$
(D) $\frac{\pi}{8}$
- 1. C.

From the problem, we know that the smallest positive root of the given function is $\frac{\pi}{6}$, and the necessary condition for an odd function is that its value at the origin is 0. Therefore, the minimum value of $\varphi$ is $\frac{\pi}{6}$.