单项选择题
Electrical supply is always needed even if only for lighting so after a ship goes into service it is extremely rare for the main bus-bars to be dead, it therefore follows that the bus-bars are continuously alive（） the life of the ship.
A.along B.will C.throughout D.for
单项选择题 The current flowing first in one direction and then in another is called（） current.
单项选择题 Shore power must be（） during dock repair.
单项选择题 The coil of wire rotating in the magnetic field produces the（）.
