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【多选题】
并励直流发电机的自励条件有（）A.
磁路中必须有剩磁
B.
电枢回路的总电阻必须小于临界电阻
C.
励磁磁动势与剩磁方向相同
D.
励磁回路的总电阻必须小于临界电阻
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举一反三
【单选题】existing very commonly or happening frequently
A.
assign
B.
submarine
C.
prevalent
D.
explicitly
【简答题】A．traditional. B．more melodic. C．very repetitive. D．commonly played.
【单选题】What are very commonly used teaching procedures and stages?
A.
Presentation, practice and production
B.
Pre-reading, while-reading and post-reading
C.
Mechanical practice and meaningful practice
D.
Both A and B
【单选题】A unit price contract is very commonly used for ( )
A.
a tunnel
B.
school buildings
C.
an apartment building
D.
a hospital
【简答题】Very __________ is a specialist capable of being an administrator. [A] commonly [B] scarcely [C] rarely [D] hardly
【单选题】What are very commonly used teaching stages?
A.
PPP
B.
PWP
C.
Mechanical practice and meaningful practice
D.
Both A and B
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