汗孔的别称是（）

A.孤府

B.玄府

C.精明之府

D.髓之府

E.血之府

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