Explain why we refer to the opportunity cost of capital, instead of just cost of capital or

Question:

Explain why we refer to the opportunity cost of capital, instead of just "cost of capital" or "discount rate." While you're at it, also explain the following statement: "The opportunity cost of capital depends on the proposed use of cash, not the source of financing."

Cost Of Capital
Cost of capital refers to the opportunity cost of making a specific investment . Cost of capital (COC) is the rate of return that a firm must earn on its project investments to maintain its market value and attract funds. COC is the required rate of...