On which of the following observations was Raymond Vernon's product life-cycle theory based?

A. The wealth and size of the U.S. market gave U.S. firms a strong incentive to develop new consumer products.

B. The high cost of U.S. labor gave U.S. firms an incentive to develop cost-saving process innovations.

C. The United States developed a very large proportion of the world's new products for most of the twentieth century and sold them first in the U.S. market.

D. The United States exports goods that heavily use skilled labor and imports heavy manufacturing products that use large amounts of capital.

E. The United States has long been a substantial exporter of agricultural goods, reflecting in part its unusual abundance of arable land.

C