Some Nations That Seek to Produce All of Their Own

Some nations that seek to produce all of their own needs face the problem that

A) ​they can deplete their natural resources faster as a result.
B) ​some industries are too small to be efficient if restricted to their domestic markets alone.
C) ​the opportunity cost of producing some of their own goods is higher than that of trading with others for them.
D) ​all of the above are true.