If a project has a net present value equal to zero, then:

A. the total of the cash inflows must equal the initial cost of the project.

B. the project earns a return exactly equal to the discount rate.

C. a decrease in the project's initial cost will cause the project to have a negative NPV.

D. any delay in receiving the projected cash inflows will cause the project to have a positive NPV.

Can you explain why it's B?