A positive demand shock causes the aggregate demand curve to undergo an ______ shift.

Writer Thomas Friedman asserts that "America is the greatest engine of innovation that has ever existed and it can't be duplicated anytime soon, because"

A. of its extreme freedom of thought. B. of its emphasis on independent thinking. C. of its steady immigration of new minds. D. of all of the factors listed.

If demand is perfectly elastic,

A. The demand curve is vertical. B. The demand curve is very steep. C. The demand curve has a zero slope. D. The demand curve is horizontal.