若互不相等的四条线段的长a、b、c、d满足
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A，根据分式的基本性质，错误；
B，右边的分子应是d+m，错误．
C，根据乘法交换律，交换两内项的位置，应是
=a c
，错误；b d
D，若
=a b
，根据分式的合比性质，得c d
=a-b b
①，c-d d
=a+b b
②．①÷②，得c+d d
=a-b a+b
．正确．c-d c+d
故选D．
阅读下面短文，根据所读内容在文后第53至第57小题的空格里填上适当的单词或短语，并将答案转写到答题卡上。 注意：每空不超过3个单词。 Thanksgiving Day Many people believe Thanksgiving is a Western holiday, but in fact, it is only an American holiday held every fourth Thursday of November although Canada holds their own unique Thanksgiving on the second Monday of October. The pattern of the Thanksgiving celebration has never changed through the years. The big family dinner is planned months ahead. Some of the family will have to travel by air and others will make long motor trips with the children. Sons and daughters away at college use their four-day holiday to go home, and employees take extra days from their work so as to be able to make the trip for the annual reunion. The Thanks-giving dinner menu today is somewhat the same as it was on Thanksgiving Day in 1863. On the dinner table, people will find apples, oranges, chestnuts and grapes. There will be pudding (布丁), mince（肉末）pie, other varieties of food and squash（鲜果汁）. The rest and most attractive among them are roast turkey and pumpkin pie. They have been the most traditional and favorite food on Thanksgiving Day throughout the years. In true Thanksgiving spirit the family circle is often enlarged to include friends known to be alone, foreign visitors, or servicemen away from home. Orphans, the aged and the homeless also have the traditional turkey dinner, provided either by some charitable (慈善的) individual or a church group. Thanksgiving Day
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