A propeller, in order to operate efficiently, must rotate at a relatively （） speed.

A.To reduce the main engine speed
B.To increase the main engine speed
C.To govern the main engine speed
D.To fix the propeller shaft

A.Two main areas of skill are involved in the construction of ship
B.There are distinct divisions in responsibilities between naval architects and marine engineers
C.Each ship will assume varying proportions according to its type
D.Ships can be divided into different categories from different perspectives

A.larger
B.equal
C.smaller
D.equivalent