单项选择题
A.no equipment in contact with sea water
B.less equipment in contact with fresh water
C.more equipment in contact with sea water
D.less equipment in contact with sea water
单项选择题 You must take good care of the drainage cock of the air control systemBecause （） leads scale formed which might malfunction the pilot control valve and other instruments.
单项选择题 You increased the （） to 150 tons that’s why the fuel oil （）.
单项选择题 Worn out ring grooves should be （） to standard dimension after being welded.