Figure 2.2 -Figure 2.2 Presents a Production Possibilities Curve for a Country

Figure 2.2
-Figure 2.2 presents a production possibilities curve for a country that can either produce highways or provide people with medical care in a given year. The opportunity cost of the fourth new highway built in a year is:

A) the sum of the opportunity costs of the first three highways built.
B) the same as the opportunity cost of the third new highway.
C) greater than the opportunity cost of the third new highway.
D) less than the opportunity cost of the third new highway.