【单选题】
The conclusion that mechanical efficiency is always () 100 percent is correct.
A、small than
B、more than
C、little than
D、less than
A、small than
B、more than
C、little than
D、less than
A、A.before the conclusion of the voyage B、B.after the conclusion of the voyage C、C.as soon as the expenditure occurs D、D.before or after the conclusion of the voyage