Which of the Following Is True

Which of the following is true?

A) The production possibilities curve indicates that it will be impossible to expand total output with the passage of time.
B) As long as resources are scarce, output cannot be increased.
C) The size of the economic pie is fixed, and therefore, if one individual has more income, others must have less.
D) Over time, the output of goods and services can be increased through human ingenuity and discovery of better ways of doing things.