When Countries Specialise in Producing Those Goods in Which They

When countries specialise in producing those goods in which they have a comparative advantage, they:

A) allocate their resources more efficiently, but they do not necessarily maximise their combined output
B) do not necessarily maximise their combined output, and they also do not necessarily allocate their resources more efficiently
C) maximise their combined output, but they do not necessarily allocate their resources more efficiently
D) maximise their combined output and allocate their resources more efficiently