In an ideal optical fiber communication system, when the bit error rate Pe is required to be , the optical pulse corresponding to each "1" code received by the optical receiver includes at least ____ photons. 
A、21
B、27
C、121
D、126

A．Eat more food.
B．Extend the masticatory time.
C．Speed up masticatory power.
D．Restore the normal function of the affected teeth.
E．None of the above.