One method for studying opportunity cost is to think in terms of

risk and ability.

pros and cons.

tradeoffs

trial and error.

The correct answer is tradeoffs

Tradeoffs are basically the understanding that in order to get one thing you have to lose another. For example, if you buy something, you lose your money but you get the thing. If you study you lose your time but you gain knowledge. Opportunity costs are tradeoffs because one thing has to be lost, which is the opportunity cost, in order to get another thing.