单项选择题
Starting air for auxiliary engines may be taken directly from the main reservoirs or through （）.
A.an auxiliary reservoir B.a controlling air bottle C.an emergency air compressor D.a main air compressor
单项选择题 Two main lubricating oil pumps are usual and are obligatory in （）.
单项选择题 In motor-ships, （）, after passing through main and motion bearings and oil cooled pistons, etcis either retained in the bedplate.
单项选择题 In motorships，there are two main circuits, （）.
