Which of the Following Statements Is True

Multiple Choice

Which of the following statements is true?

A) In a world of efficiently used scarce resources,more of one good necessarily means less of some other good.
B) The law of increasing opportunity costs assumes that all people have the same ability to produce goods.
C) Efficiency implies that it is impossible to get more of one good without getting less of another.
D) Even if a country has unemployed resources,it can still be operating on its production possibilities frontier (PPF) .
E) a and c