PLEASE HELP What is opportunity cost?

the limited availability of goods or services
a benefit lost when choosing between two options
the resources used to produce finished goods or services
a system of directly exchanging goods or services for other goods or services

Which situation from a novel best reflects the following theme? prejudice can be found in unexpected places and is always hurtful to those exposed to it. a. community members admire a public figure until a child exposes him as a fraud b. witnesses to a violent attack remain quiet for fear of endangering their families o c. a talented doctor cannot get work in a neytown because he is an "outsider." d. a couple tries to keep their romance alive across a great distance but fails.