The prefix hydro-,as in the term hydrotherapy,means:

A) good.
B) water.
C) difficult.
D) self.

Hydro-

A prefix indicating relation to water.

Hydrotherapy

The use of water in the treatment of different conditions, including arthritis and related rheumatic complaints.

Water

A colorless, odorless, tasteless liquid that forms the seas, lakes, rivers, and rain, and is the basis of the fluids of living organisms.