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【单选题】

For the transportation problem, the potential method and the closed loop method are used to calculate the test number, then the result ( )

A.
must be the same
B.
must be different
C.
may not be exactly the same
D.
no connection
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参考答案:
参考解析:
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【单选题】If the synchronous generator connected in parallel to the infinite power grid keeps the active power output unchanged and changes from over excitation operation state to under excitation operation sta...

A.
The Angle of changes from positive to negative and the Angle of from large to small;
B.
The Angle of changes from positive to negative and the Angle of from small to large;
C.
The Angle of Angle changes from negative to positive, and Angle decreases from large to small;
D.
The Angle of changes from negative to positive and the Angle of from small to large.

【单选题】What makes the sand here colorful?

A.
trace elements and minerals
B.
the change of seasons and weather
C.
intensity of the sun
D.
All above

【单选题】Synchronous generators parallel to the infinite grid must ( ) to increase ( ) to ( ) while keeping the load current as the rated value.

A.
Increase the excitation current and the input torque;
B.
Increase the excitation current and decrease the input torque;
C.
Reduce the excitation current and increase the input torque;
D.
Reduce the excitation current and increase the input torque.

【单选题】Most of the sand here is ______.

A.
quartz sand
B.
beach sand
C.
artificial sand
D.
dry sand