An alternator switchboard has a synchroscope and synchronizing lamps, if the synchroscope

A. The breaker should be closed when one synchronizing lamp is dark and the other is bright
B. The breaker should be closed when both synchronizing lamps are bright
C. The frequency meter should be used to determine that the incoming alternator frequency is slightly higher than the bus
D. A portable phase sequence indicator must be used to verify the information from the lamps