Final answer:
The opportunity cost of entering a baseball pool with $20 is the value you could obtain by spending the money on buying something else.
Step-by-step explanation:
The opportunity cost of entering a baseball pool with $20 is the value you could obtain by spending the money on buying something else. Option B, 'The value you could obtain by spending the money on buying something else,' is the correct answer. Opportunity cost refers to the value of the best alternative that is forgone when a decision is made. In this case, if you choose to enter the baseball pool, you are giving up the opportunity to use that money for another purpose, such as buying something you need or saving it.