What has motivated American firms to move their operations to foreign countries?

A. Trade barriers, lower production costs, access to skilled workers, and U.S. tax deferral

B. Trade barriers, lower production costs, access to natural resources, and manufacturing

C. Import tariffs, foreign unions, foreign technology, and expropriation

D. Lower production costs, U.S. tax deferral, access to natural resources, manufacturing, and expropriation