Distributor :

1. A distributor is a conductor from which tapping are taken for supply to the consumer.

2. Current through distributor is not constant because tapping are taken at various places along its length.

3. While designing a distributor, voltage drop is main consideration since the statutory limit of voltage variation ± 6% of rated value at consumer terminal.

Feeder : A feeder is a conductor which connects the sub-station to the area where power is to be distributed. Generally no tapping are taken from the feeder so that current in it remains the same throughout the set of operation.

1. The main consideration in the design of a feeder is the current carrying capacity.

Service Mains : A service mains is the generally a small cable which connects the distributor to the consumer terminals.

Hence, the correct option is (B).