试述胸膜腔积液的A超诊断依据。
参考答案：在胸膜腔体表投影范围内出现液性平段，液平段后方为肺波反射。
I paid him ￡50 for the painting, but its true ______ must be at least ￡500.
A．price
B．money
C．value
D．importance
简述筹资结构与筹资战略的关系。
