Which of the following statements is true?

a. An opportunity cost is what must be given up in order to get something else.

b. The three fundamental economic questions refer to What to produce? How to produce? and When to produce?

c. The term “investment” refers to the purchase of stocks and bonds and other financial securities.

d. The law of increasing opportunity cost implies that as production of one type of good is expanded, then fewer and fewer of other goods must be given up.