单项选择题
A.the control rod
B.the hunting gear
C.the floating ring
D.the tiller arm
单项选择题 Additional heat extraction from the exhaust gases can be effected by adding an （） section to the unit in plants.
单项选择题 Oil water separators are used to ensure that ships don’t discharge oil when （） bilge water.
单项选择题 In general, （） is suitable for delivering small quantifies at high pressure.