When something is on fire, people throw sand on it to put out the fire. The main use of the sand is to _________.

A．protect the thing on fire

B．add weigh to the thing on fire

C．keep the air away from the thing on fire

D．lower the temperature of the thing on fire

针灸治疗中心性视网膜炎肝肾亏虚者，除基本处方外，可加（）。

A.肝俞、肾俞

B.肝俞、行间

C.太溪、行间

D.太溪、三阴交

E.三阴交、足三里