What does a production possibilities curve represent?
a. a combination of price and demand of goods and services
b.
a combination of the goods produced before and after a change in a factor of production
c. a combination of two factors of production used to produce a single good or service
d.
a combination of two goods that can be produced using limited resources

Combination of two goods that can be produced using limited resources

Explanation:

A production possibilities curve is a graphical representation of the alternative combinations of goods and services an economy can produce. Considering the fact that an economy's factors of production are scarce; they can not produce an unlimited quantity of goods and services, a production curve is crucial in determining the alternative combinations of goods and services. For example if the curve is a straight line, it means the for every unit of good y relinquished, an additional unit of good x can be produced. 

"social stratification refers to the way people are ranked and ordered in society. in western societies, stratification is primarily seen and understood as a result of socioeconomic status, which produces a hierarchy in which access to resources, and possession of them, increases from the lower to the upper strata"