Only when the villagers were faced with water shortage___       how serious the problem of water pollution was．

A．did they realize

B．will they realize

C．they did realize

D．were they realized

对科学与技术的关系表述正确的一项是（）

A．科学与技术分化，科学对技术的影响甚微

B．相互制约、相互促进的关系

C．科学家开始关心生产技术

D．技术始终促进科学的发展