单项选择题 A sight glass is installed in the liquid line to indicate the condition of the refrigerant charge and may also indicate the （）.

单项选择题 If one hydraulic pump of an electro-hydraulic steering unit falls, the vessels steering can be initially and best maintained by using the （）.

单项选择题 The bilge system has been performing well; however, the aft starboard engine room bilgewell suddenly fails to be pumped outWhich of the following should be done first to determine the cause?（）