单选题 A DC generator is used to supply direct current in order to maintain an AC generator field and is known as a/an ____.

单选题 The process of removing moisture from air is known as ____.

单选题 Both fuel oils and lubricating oils require ____ before passing to the engine.

单选题 An electron has a ____ charge.

单选题 The oil sludge is burnt in the ____ onboard. I'll show you the ashes.

单选题 The voltages most commonly adopted for a.c. system are either 440V or 220V ____.

单选题 ____ are used for cargo handling.

单选题 The current flowing first in one direction and then in another is called ____ current.

单选题 ____ is the circulation and refreshing of the air in a space without necessarily a change of temperature.