Which of the following statements is true?

A. The dealers of stock are not allowed to make money on the difference between what they buy the stock for and what they sell it for.

B. A bear market is a prolonged rising market, one in which stock prices in general are increasing.

C. The ask price is the price at which a dealer is willing to sell, and the bid price is the price at which a dealer is willing to buy.

D. A bull market is a prolonged declining market, one in which stock prices in general are decreasing.