[单项选择]The physical distribution of products has two primary aspects: transportation and storage. Both aspects are highly developed and specialized phases of marketing. The costs of both transporting and storing are built into the prices of products. Transportation can be by truck, railways, ship, or barge. For some items, such as exotic plants and flowers, or when rapid delivery is essential, air freight may be used. Storage, or warehousing, is a necessary function because production and consumption of goods rarely match: items generally are not sold as quickly as they are made. Inventories build up, both in warehouses and at retail establishments, before the foods are sold. The transportation function is involved in bringing goods to a warehouse and taking them from it to retail stores. Storage performs the service of stabilizing market price. If, for example, no agricultural product could be stored, all food would have to be put on the market immediately. This would, of course, create a glut and lower prices drastically. There would be an immediate benefit to consumers, but in the long run they would suffer. Farmers, because of low prices, would be forced off the land, and the amount of food produced would decrease. This, in turn, would raise consumer prices. Warehouses for storage are of several types. Private warehouses are owned by manufacturers. Public warehouses, in spite of their name, are privately owned facilities, but they are independent of manufacturer ownership. General-merchandise warehouses store a great variety of products. Cold-storage warehouses store perishable goods, especially food products. Grain elevators are a kind of warehouse used to keep wheat and other grains from spoiling. A bonded warehouse is one that stores foods, frequently imported, on which taxes must be paid before they are sold. Cigarettes and alcoholic beverages are common examples. The distribution center is a more recently developed kind of warehouse. Many large companies have several manufacturing plants, sometimes located outside the country. Each plant does not make every company product but specializes in one or more of them. The distribution center allows a manufacturer to bring together all product lines in one place. Its purpose is to minimize storage and to ease the flow of goods from manufacturers to retailers rather than build up extensive inventories. It reduces costs by speeding up product turnover. Very large corporations will have several distribution centers regionally or internationally based.The main subject of this passage is______.
A. transportation and storage
B. storage of products
C. distribution center
D. two main aspects of product distribution