Answer:
2) We must decrease the production of food. This foregone food production represents the opportunity cost of the increase in shelter.
Step-by-step explanation:
The production possibilities curve shows how much we lose when we decide to produce something else. For example, if you decide to produce only food, you will not be able to produce any shelter, so the opportunity cost of producing only food is the lost benefits from producing shelter. The more you produce of some good, the less you will produce of the other good.
In this case, the opportunity cost of producing shelter is the lost benefit from producing food.