Dmitri is training for a triathlon, a timed race that combines swimming, biking, and running. Consider the following sentence: In order to swim for an hour, Dmitri must take time away from work, where he earns $12 per hour. This is in addition to paying a $5 entrance fee for the pool. Which basic principle of individual choice do these statements best illustrate? People usually exploit opportunities to make themselves better off. Trade can make everyone better offMarkets are usually a good way to organize economic activityThe cost of something is what you give up to get it

The true cost of an item is opportunity cost.

Explanation:

Opportunity cost is cost of doing something better, and for doing so the cost is earnings or advantages of the activity foregone.

This is the basic principle of individual choice, these statements best illustrate. Here, the opportunity of earning $12 per hour is foregone, in order to train for a triathlon, although total cost inclusive of opportunity cost will be higher as $5 for entrance is also to be paid in addition of earnings foregone.

Correct statement for the above situation is:

The true cost of an item is opportunity cost.