On December​ 15, 2017, a company receives an order from a customer for services to be performed on December​ 28, 2017. Due to a backlog of​ orders, the company does not perform the services until January​ 3, 2018. The customer pays for the services on January​ 6, 2018. The revenue principle requires the revenue to be recorded by the company​ on:
A. December​ 15, 2017.
B. December​ 28, 2017.
C. January​ 3, 2018.
D. January​ 6, 2018.