Revenue should be recognized when a. the customer charges an order b. cash is received c. the customer places an order d. the service is performed

d. the service is performed

Explanation:

According to the revenue recognition principle, the revenue is recognized when it is earned or realized not when the cash is received. It is based on the accrual basis of accounting. It does not depend upon the cash.  

In other words, whether cash is received or not but the revenue is recognized on the books when the service is performed.

answer utilities; more money you have to pay out ; )