Which of the following statements is correct?

A. when investors increase their required rate of return, the cost of capital increases simultaneously.

B. The minimum rate of return necessary to attract an investor to purchase or hold a security is called the cost of capital.

C. The weighted average cost of capital is computed using before tax costs of each of the sources of financing that a firm uses to finance a project.

D. The firm's weighted average cost of capital includes the cost of common stock, preferred stock and retained earning, but not debt.