单项选择题
The structural members of the hull extending in a fore and aft direction are called （）.
A.frames B.joiners C.longitudinals D.knees
单项选择题 Increased internal leakage, in addition to poor hydraulic system response,and inadequate lubrication, is the result of （）.
单项选择题 Most solenoid valves are actuated by （）.
单项选择题 When normal operating pressure is applied to the hydraulic oil used in a high-pressure system, the oil （）.
