Which of the following statements about opportunity costs is false?

a. The opportunity cost rate to be applied to any investment is the rate of return that could be earned on alternative investments of similar risk.

b. In general, higher-risk investments should have higher opportunity costs than lower-risk investments.

c. The opportunity cost rate typically is applied in discounting future cash flows.

d. Say you just inherited $10,000. Because this money cost you nothing, it has an opportunity cost rate of zero.