【单选题】Consider a PPF for tapes and soda. If the opportunity cost of a tape increases as the quantity of tapes produced increases and also the opportunity cost of a soda increases as the quantity of soda pro...
A.
a straight, downward-sloping line.
B.
a straight, upward-sloping line.
C.
bowed outward.
D.
All of the above are possible and more information is needed to determine which answer is correct.