The important factor in a private-enterprise economy is that individuals are allowed to own productive resources (private property), and they are permitted to hire labor, gain control over natural resources, and produce goods and services for sale at a profit. In the American economy, the concept of private property embraces not only the ownership of productive resources but also certain rights, including the right to determine the price of a product or to make a free contract with another private individual.

　　51. In Line 11, Para 1, "the desire of individuals to maximize their incomes" means__.

　　[A] Americans are never satisfied with their incomes

　　[B] Americans tend to overstate their incomes

　　[C] Americans want to have their incomes increased

　　[D] Americans want to increase the purchasing power of their incomes

　　52. The first two &sentences in the second paragraph tell us that__.

　　[A] producers can satisfy the consumers by mechanized production

　　[B] consumers can express their demands through producers

　　[C] producers decide the prices of products

　　[D] supply and demand regulate prices

　　53. According to the passage, a private-enterprise economy is characterized by__.