The stock market boom of the 1920s occurred in part because the demand

The stock market boom of the 1920s occurred in part because the demand for stocks increased. The source of this demand increase originated from whom?

(a) Ordinary workers who experienced rising wages and now had incentive to invest in the stock market, thus driving up stock prices.
(b) The people in the upper income strata; they received a high percentage of the increase in realized income during the 1920s and invested much of it in the stock market.
(c) Farmers who, finding agriculture increasingly unprofitable, began investing in the stock market rather than in farm land and equipment.
(d) Foreign investors who were optimistic about America’s future and accordingly invested in American stocks.

ANSWER

(b)