Answer: B. Adams received for services to be performed in a later period.
Step-by-step explanation:
Unearned revenue represents cash paid by a customer for services that have not yet been done or goods that have not yet been delivered.
It is credited because it represents a liability as the company owes the customer the services or goods they paid for.
Adams here received cash for services that have not yet been performed which is why it was sent to the unearned revenue account and debited to cash to show that cash was received.