单项选择题
A.overboard
B.a bilge well
C.a slop tank
D.a hot well
单项选择题 For the intermediate condition, thermostats must be correctly set （）.
单项选择题 Most air conditioning units have （） for adjusting the ratio of recirculated fresh airCare must be taken not to reduce the fresh air so that stuffiness or smells arise.
单项选择题 In extreme weather conditions, either hot or cold, control of the air conditioning plant presents （） difficulties.