Since opportunity cost is defined as the cost of any activity measured in terms of the best alternative activity, which is forgone, in this case, the opportunity cost can be a field for students to play around or a land where a library can be built. Another example would be the opportunity cost of coming to school. This answer will be the time enjoyed going to the cinema or time spent with your partner. Hence, the opportunity cost of coming to school will be the cost of not going to cinema and spending time with your partner.