In QBO,Single Time Activity Is One Way to Track Time

In QBO,Single Time Activity is one way to track time.It is used to:

A) invoice customers for billable time related to specific projects.
B) enter time billable to specific customers.Then time is added to the customer's invoice.
C) enter time worked by each specific employee during a week.
D) time one activity and enter the time data.The time is then recorded on the employee's weekly timesheet.