Before doing any work on a hydraulic system equipped with accumulators, you should
A.drain the accumulators and purge with oxygen
B.bleed off all stored energy from the accumulators completely
C.charge the accumulators to prevent system energy loss
D.pump the hydraulic fluid into the accumulators to prevent fluid loss

A.A.petroleum
B.phosgene
C.water
D.carbon

A.A.opposite
B.the
C.negative
D.positive

A.勒·柯布西耶(LeCorbusier)、路易斯·康(LouisIsadoreKahn)、路易斯·康(LouisIsadoreKahn)、路易斯·康(LouisIsadoreKahn)
B.密斯·凡·德·罗(MiesVanDerRohe)、勒·柯布西耶(LeCorbusier)、路易斯·康(LouisIsadoreKahn)
C.勒·柯布西耶(LeCorbusier)、勒·柯布西耶(LeCorbusier)、勒·柯布西耶(LeCorbusier)
D.密斯·凡·德·罗(MiesVanDerRohe)、W.格罗皮乌斯(WalterGropius)、勒·柯布西耶(LeCorbusier)