If People Stand to Produce at Lower Cost When Specializing

If people stand to produce at lower cost when specializing and producing in larger quantities

A) they cannot gain from trade because each one is just as potentially productive as another.
B) they cannot gain from trade because most people's wants can be easily satisfied with what they can produce themselves.
C) they cannot gain from trade if they have similar tastes.
D) they can gain from trade by specializing and increasing productivity.