One economic truism is that any nation's restriction of imports will ultimately lead to

All of the following encourage increases in technological progress EXCEPT

A) closed economies. B) larger markets through free trade. C) the possibility of monopoly profits. D) the ability to patent a new invention.

Which of the following have been suggested as sources of economic profit?

a. exercise of monopoly power by firms b. accepting a large degree of risk c. successful innovation d. All of the above are correct.