发电机发出的电能是由（）转换来的。
A.动能；
B.机械能；
C.化学能；
D.光能;
参考答案：B
A court-martial has but recently decided to acquit him.
A．declare he is not guilty
B．pardon him
C．condemn him
D．persecute him,
当速度T=1/60 s时；TV=( )。
A．5
B．4
C．6
D．8
