21. а) Раскройте скобки и употребите глаголы в соответствующей форме. Each market (to describe) by two main characteristics:

Each market describes by two main characteristics: the good itself and the geographic area. Each market includes only the goods which satisfy the same consumers\' needs. For example, two brands of English muffins are in the same market, but televisions and cars are in different markets. Nintendo and Sony electronic games aren\'t identical goods, but they both are included in the market for games. The second characteristic of a market, geographic area, is also of importance for describing markets. As bread is baked and sold usually in a particular place, the Chicago bread market and the Detroit bread market are different markets. As microwave ovens are transported nationwide, the market for a particular brand is the entire country or several countries.