Consider the following scenario: Neha is training for a triathlon, a timed race that combines swimming, biking, and running. Each hour she spends swimming is an hour that she can't spend biking or running.

Which basic principle of individual choice does this sentence best illustrate?

= People usually exploit opportunities to make themselves better off. = All choices have opportunity costs. = Neha can use time most efficiently by spending the same amounts of time on swimming, biking, and running. = Neha has an incentive to spend more time on swimming than on biking or running.