Which of the Following Best Describes What Rate of Return

Which of the following best describes what rate of return should be used when finding the present value of a series of cash flows?

A) Free cash flows should be discounted at the firm's average cost of debt capital to find the value of its operations.
B) Free cash flows should be discounted at the firm's weighted average cost of capital to find the value of its operations.
C) Free cash flows should be discounted at the firm's cost of equity capital (preferred and common) to find the value of its operations.
D) Free cash flows should be discounted at the firm's cost of preferred equity capital and pre-tax cost of debt capital to find the value of its operations.