题目: 控制阀由哪几种阀组成,各起什么作用? 答案: 参考答案:控制阀由液控单向阀和安全阀组成。液控单向阀主要是用来闭锁立柱或千斤顶工作腔中的液体,保证支撑的稳定可靠。安全阀的作用是防止立柱或支架过载,保证支架安全工作。
题型:选择题 My parents ________ in Hong Kong.They were born there and have never lived anywhere else.A.liveB.livedC.were livingD.will live 查看答案
题型:选择题 We must keep our room clean. Dirt and disease go _____ you know.A.from time to timeB.hand in handC.step by stepD.one after another 查看答案