The production possibilities curve demonstrates the basic economic principle that

a. economies are always efficient
b. assuming full employment, supply will always determine demand
c. assuming full employment, an economy is efficient only when the production of capital goods in a particular year is greater than the production of consumption goodsin that year
d. assuming full employment, to produce more of any one thing, the economy must produce less of at least one other good
e. the production of more consumption goods this year requires the production of morecapital goods this year

D