I think its letter C? correct me if wrong please!! Thanks in advance :))

upon its entry into WWI, U. S. didnt have a military large enough to sustain the demand of deployment. U. S. didnt have enough material//men to fight effectively.

-how did the U. S. government fix this?

A. by signing the treaty of versailles?

B. by stealing the zimmerman telegram?

C. by passing the selective service act?

D. by passing the G. I Bill?