问题描述：
[单选]
The successful operation of any engine or machine and（）depend on effective lubrication．
A．their no trouble period
B．their freely trouble period
C．its free trouble life
D．its trouble-free life
参考答案：查看无
答案解析：无
☆收藏
答案解析：无
☆收藏
上一篇：The supercharger takes air out of the surrounding atmosphere and then feeds it to the engine’s（）．
下一篇：The starting air system usually has（）to prevent starting if anything is not in order．
- 我要回答: 网友(216.73.216.168)
- 热门题目: 1.在采用并联措施提高系统的可靠 2.串联系统的部件数目n与工作时 3.假设某一中央冷却系统中设有三