The theory underlying demand and supply curves assumes that, all other things unchanged, the primary variable that assures the equality of the quantities demanded and supplied is:

In 2008, as the economy moved into a recession,

A) cyclical unemployment increased. B) structural unemployment decreased. C) natural unemployment decreased. D) frictional unemployment was not affected. E) the number of marginally attached workers decreased.

The De Beers Company, one of the longest-lived monopolies, is facing increasing competition. One source of competition comes from people who might resell their previously owned diamonds. Why is De Beers worried that people might resell their previously

owned diamonds? A) because De Beers will not be able to guarantee the quality of previously owned diamonds and fears that its reputation might be harmed B) because the availability of previously owned diamonds would increase the market demand for diamonds and dilute De Beers' monopoly C) because previously owned diamonds would be a close substitute to newly mined diamonds and would therefore reduce De Beers' market power D) because the availability of previously owned diamonds would make the market demand curve for diamonds more inelastic and force De Beers to lower its price