Which of the following sentences is written in passive voice? 

A. Water should be drunk throughout the day as the best way to hydrate your body. 
B. Abe drinks water throughout the day because it is the best way to keep the body hydrated. 
C. Drinking water throughout the day is the best way to hydrate your body.
D. You should drink water throughout the day as it is the best way to keep the body hydrated.