Developing Countries Often Claim That Their "Commodity Terms of Trade

Developing countries often claim that their "commodity terms of trade" have fallen over the long run. This means that (with P_x = export price index, P_m = import price index, Q_x = export quantity index, and Q_m = import quantity index) the developing countries think that there has been a decline in their __________.

A) (P_m/P_x) .Q_m
B) P_m/P_x
C) P_x/P_m
D) (P_x/P_m) .Q_x