Paul had three ways to use his allowance money: spend, save, or donate. He decided to donate his money to charity. Any value given up by not choosing to spend or save the money is the _____.
a. opportunity cost
b. marginal cost
c. trade-off
This would be the opportunity cost: the cost on missing out on different opportunities once one opportunity is chosen. So if you choose A over B, the opportunity cost is the gain you could have had if you'd chosen B (even if you anyway couldn't have chosen both in the first place!)
