In the presence of external economies of scale, trade
A.
may or may not improve welfare in both countries.
B.
will unambiguously improves welfare in both countries.
C.
will unambiguously worsens welfare in both countries.
D.
will unambiguously worsen welfare in the exporting country and improve welfare in the importing country.
E.
will unambiguously improve welfare in the exporting country and worsen welfare in the importing country.