A DC generator is used to supply direct current in order to maintain an AC generator field and is known as a/an （）

A.coulombs per second
B.revolutions per second
C.revolutions per minute
D.cycles per second

A.slightly less than the oncoming generator frequency
B.the same as the bus frequency
C.slightly greater than the bus frequency
D.the same as the bus voltage

A."slow" direction, just before the 12 o'clock position
B."fast" direction, just after the 12 o'clock position
C."fast" direction, just before the 12 o'clock position
D."slow" direction, just after the 12 o'clock position