原发性肾小球肾病性水肿的最主要机制是()

A．蛋白尿史，血浆蛋白降低而致胶体渗透压下降

B．继发性醛固酮及血管升压素增多

C．心功能不全

D．毛细血管滤过率下降

E．肾小球滤过率下降

The series of valves used to control the return flow in well control operations is called the（）.

A.valve assembly

B.standpipe manifold

C.accumulator manifold

D.choke manifold