Which of the following sayings best reflects the concept of opportunity costs

The greatest appeal of U.S. Treasury securities is that

A) they have high yields. B) they have no default risk. C) the U.S. Treasury will repurchase them at any time. D) their market prices fluctuate very little.

Between 1921 and 1929, general prices as measured by wholesale or consumer prices

(a) were stable overall. (b) fell dramatically. (c) increased moderately. (d) increased significantly.