"There are three hydraulic systems on 737, system A and system B are full-time operating systems during flight that share responsibility for all hydraulically powered components.The standby system is operated only on the ground ." The above sentence means“波音737装有三个单独的液压系统，飞行中，A系统和B系统总是处于工作状态，共同负责所有液压部件的操纵。备用系统只在地面操作时启动。”
A.1
正确答案是A