Which of the following most accurately indicates the implications of an economy's production possibilities curve?

a. If all the resources of an economy are being used efficiently, more of one good can be produced only if less of another good is produced.
b. If all the resources of an economy are being used efficiently, it is generally possible to produce more of one good without having to sacrifice the production of other goods.
c. Over time, it is generally impossible for a country to expand its production of goods.
d. An economy will automatically move toward a point that lies outside of the production possibilities constraint unless proper government policy constrains production.

a