Juanita is training for a triathlon, a timed race that combines swimming, biking, and running. Consider the following sentence: Because her pool sessions are helping her swim more quickly, Juanita plans to reduce by 1 hour per week the time she spends training on the bike and increase by 1 hour the time she spends in the swimming pool; however, her husband says that she should stop doing any biking and running and spend all 20 hours per week in the pool. Which basic principle of individual choice does Juanita's plan illustrate that her husband's advice does not?

Many decisions are made on the margin.

Explanation:

The options include:

A. People usually exploit opportunities to make themselves better off.

B. Resources are scarce.

C. Many decisions are made on the margin.

D. All costs are opportunity costs.

The basic principle of individual choice that Juanita's plan illustrate that her husband's advice does not is that many decisions are made on the margin.

From the question, we are informed that Juanita plans to reduce by 1 hour per week the time she spends training on the bike and increase by 1 hour the time she spends in the swimming pool. This shows the effect of margin. Margin simply means something extra.

While Juanita wante to spend extra time swimming, while her husband wants her to spend the whole 20 hours in the pool. Their decisions are both based on margin.