At what stage of the product life-cycle theory does production within other advanced countries begin to limit the potential for exports from the United States? Multiple Choice
a. when the U.S. firms set up production units in the advanced nations to meet rapidly growing demand
b. when the impact of differences in technology on productivity gets neutralized
c. when there is limited initial demand in the developing countries
d. when the demand in other advanced countries is limited to high-income groups
e. when the demand is starting to grow rapidly in the United States