Among the Conclusions of the Many Studies of Technology Diffusion

Among the conclusions of the many studies of technology diffusion is/are:

A) foreign countries are the principal source of new technologies for all but the very largest economies.
B) small developed economies and all developing economies depend on foreign sources for nearly all of their technological change.
C) in general it takes longer for technology to move across borders than within countries.
D) All of the above.
E) None of the above.