单项选择题

There is something hard to resist about cherries. The small red fruit is a popular seasonal food around the world. Cherries are thought to be native to western Asia. It is a member of the same family of plants as the rose. It is closely related to the plum. Like cherry trees, plum trees also flower in early spring.
There are two major kinds of cherries harvested in the world: sweet and sour. Sour cherries are not eaten fresh because they contain little sugar. Instead, they are processed to make prepared foods like jellies and pies and to make alcoholic drinks. The United States is a major producer of sour cherries. Among the states, Michigan is the top producer. Russia, Poland and Turkey are other important cherry-producing nations. Sweet cherries contain much more sugar than their sour relatives and are usually eaten fresh. Washington State is the biggest American producer, followed by California and Oregon. The United States, Iran and Turkey are major producers of sweet cherries. Fresh cherries do not store well. They must reach market as soon as possible. So they cost more than many other kinds of fresh fruit.
Farmers produce different kinds of cherries through the process of grafting(嫁接). They take cuttings from existing trees and join them to related trees. The cuttings grow into the root stock, so the two kinds of trees grow as one.
Cherry trees are also valued for their springtime blossoms. Cherry blossoms are popular in many parts of Asia and Europe, especially in Japan. But Washington, D. C. , has some of the most famous cherry trees in the world. Japan gave the United States 3,500 cherry trees in 1912 as a gift of friendship. Years later Japan gave another gift of 3,800 trees. In the early nineteen eighties, the United States provided Japan with cuttings to help replace Japanese trees lost in a flood.

Fresh cherries are usually expensive in the market, because ().

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