单项选择题
The starting air system usually has （） to prevent starting if anything is not in order.
A.drain cocks B.vent valves C.counteracts D.interlocks
单项选择题 The space between cylinder liner and jacket is called （）.
单项选择题 The shells are secured by means of bearing caps and studs, the necessary clearance being provided by means of （） of different thickness.
