为自己加油

Hydraulic System A pressure is supplied directly to the landing gear _______(转换活门) which ______ （通过旁路）to allow system A pressure to the selector valve for normal extension and retraction of the landing gear and nose wheel steering.

A.shutoff valve, bypass;
B.check valve, is biased ;
C.transfer valve ，is biased ;
D.transfer valve ，is routed;