Prepare yourself for the worst.

The correct answer is C.

A. “You be prepared for the worst” is grammatically incorrect. The correct way to say this would be “You should be prepared for the worst.”

B. “The worst should be prepared by yourself” is also grammatically incorrect. The correct way to say this would be “You should prepare yourself for the worst.”

C. “Be prepared for the worst” is the most concise and grammatically correct option. It is also the most direct and to the point.

D. “For the worst, preparation should be made by you” is grammatically correct, but it is wordier and less direct than option C.