Answer: 2) increasing opportunity costs
Step-by-step explanation:
The Production Possibilities Frontier (PPF) measures how much of one good an economy would have to give up to be able to produce more of another good.
Resources in the economy are scarce so a trade-off needs to be made to determine how much resources would go into one good and how much into the other. This is why when more resources go to one good, less of the other is produced.
This is what the PPF shows. As we produce one more of one good, we produce less of the other good meaning the opportunity cost ( not producing the other good) of producing more of one good increases as we keep producing it.