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问题 填空题

已知A={x|x为矩形}，B={x|x为菱形}，则A∩B=______．

答案

∵A={x|x为矩形}，∴其元素的几何特征是有一个角为直角的平行四边形，

∵B={x|x为菱形}，∴其元素的几何特征是邻边相等的平行四边形，

由交集的性质，A∩B中元素的特征是有一个角是直角且邻边相等的平行四边形，这样的图形是正方形，

故A∩B={x|x为正方形}

故答案为 {x|x为正方形}

单项选择题



The DNA test found the murder was a 14-year-old boy. True False
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单项选择题

In the United States, the first day nursery was opened in 1854. Nurseries were established in various areas during the (91) half of the 19th century; most of (92) were charitable. Both in Europe and in the U. S. , the day-nursery movement received great (93) during the First World War, when (94) of manpower caused the industrial employment of unprecedented numbers of women. In some European countries nurseries were established (95) in munitions (军火)plants, under direct government sponsorship. (96) the number of nurseries in the U.S. also rose (97) , this rise was accomplished without government aid of any kind. During the years following the First World War, (98) , Federal, State, and local governments gradually began to exercise a measure of control (99) the day nurseries by (100) them and by inspecting and regulating the conditions within the nurseries.
The (101) of the Second World War was quickly followed by an increase in the number of day nurseries in almost all countries, as women were (102) called upon to replace men in the factories. On this (103) the U. S. government immediately came to the support of the nursery schools, (104) $6,000,000 in July, 1942, for a nursery school program for the children of working mothers. Many States and local communities (105) this Federal aid. By the end of the war, in August, 1945, more than 100,000 children were being cared (106) in day-care centers receiving Federal (107) Soon afterward, the Federal government (108) cut down its expenditures for this purpose and later (109) them, causing a sharp drop in the number of nursery schools in operation. However, the expectation that most employed mothers would leave their (110) at the end of the war was only partly fulfilled.

A．formulating

B．labeling

C．patenting

D．licensing
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