人类能听到的声音频率f不低于20赫兹，不高于2000赫兹，请写出人类能听到的声音

相同型号水泵并联时，流量增加，（）不变。

“文章本无成，妙手偶得之”出自谁之口？（）

A、杜甫

B、李白

C、陶渊明

D、杜牧

如图所示，出租汽车驾驶员在运营过程中遇受伤乘客，应（）

A.额外收取服务费用

B.无视其乘车需求，加速通过

C.无偿提供租车服务

D.不得以任何理由拒载

American Thanksgivings According to tradition, the first American Thanksgiving was celebrated in 1621 by the English Pilgrims who had founded the Plymouth Colony, now in the state of Massachusetts. The an important part of American colonial history, there is no evidence that any of the participants thought of the feast as a thanksgiving celebration. Two years later, during a period of drought, a day of fasting and prayer was changed to one of thanksgiving because rains came during the prayers. Gradually the custom prevailed among New Englanders to annually celebrate Thanksgiving after the harvest. Colonial governments and, later, state governments took up the Puritan custom of designating thanksgiving days to commemorate various public events. Gradually the tradition of holding annual thanksgiving holidays spread throughout New England and into other states. During the American Revolution (1775—1783 ) the Continental Congress proclaimed a national day of thanksgiving following the American victory at the Baffle of Saratoga in 1777.U.S. President George Washington proclaimed another day of thanksgiving in 1789 in honor of the ratification of the Constitution of the United States. In 1817 New York State adopted Thanksgiving Day as an annual custom, and many other states soon did the same. Most of the state celebrations were held in November, but not always on the same day. In 1863, during the American Civil War (1861—1865 ), President Abraham Lincoln proclaimed the last Thursday in November Thanksgiving Day in order to bolster the Union’s morale. After the war, Congress established Thanksgiving as a national holiday, but widespread national observance caught on only gradually. Many Southerners saw the new holiday as an attempt to impose Northern customs on them. However, in the late 19th century Thanksgiving’s emphasis on home and family appealed to many people throughout the United States. As a distinctly American holiday, Thanksgiving was also considered an introduction to American values for the millions of immigrants then entering the country. During the 20th century, as the population of the United States became increasingly urban, new Thanksgiving traditions emerged that catered to city dwellers. The day after Thanksgiving gradually became known as the first day of the Christmas shopping season. To attract customers, large retailers such as Macy’s in New York City and Gimbel’s in Philadelphia, Pennsylvania, began to sponsor lavish parades. By 1934 the Macy’s parade, featuring richly decorated floats and gigantic balloons, attracted more than one million spectators annually.