Jim couldn’t understand how the machine worked until his friends____ how to use it.

A．promised

B．explained

C．thought

D．heard

叩诊移动性浊音阳性，提示腹腔内游离腹水达（）。

A.500mL以上

B.1000mL以上

C.1500mL以上

D.2000mL以上

E.2500mL以上