单项选择题
A.without the necessity of manually adjusting the lines
B.without the necessity of automatically adjusting the lines
C.with the necessity of manually adjusting the lines
D.with the un-necessity of automatically adjusting the lines
单项选择题 （）is put into use in the late years to maintain a preset tension in a mooring line after a ship has been tied up at a pier.
单项选择题 However fast or slow the combustion rate, it is still a （） between carbon, hydrogen, sulphur and oxygen that releases heat.
单项选择题 The trend nowadays is to build the frame box as a separate fabricated construction and then, after stress relieving and machining the mating surfaces, to mount it on the （）.This has the advantage of saving weight.