The word "depleted" (Line 1, Para. 1) possibly means"________".

A．the use of water is a completely new concept
B．the sea has long been used as a way of power
C．water is a source of energy far more economical than any other energies
D．water, if properly handled, may present a promising solution to energy crisis

A．believed in a particular religion
B．were reluctant to change their established belief in materialism
C．accepted one kind of political principle
D．gradually began to accept a belief of simplicity