当液压油箱处于过压时，油箱增压系统是通过哪项实现保护油箱的（）
A.单向活门
B.地面充气活门
C.油箱释压活门
D.过压释压活门
参考答案：D
________ in health，he persisted in doing the experiment. [ ]
A．As he was poor
B．Poor as he was
C．Poor was he
D．Poor he was though
列控中心与计算机联锁系统之间通信的报文是信号降级和进路信息报文
