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问题 选择题

下列四个命题中，假命题的是（    ）.（考查特殊四边形的判定）

A．有三个角是直角的四边形是矩形；

B．对角线互相垂直平分且相等的四边形是正方形；

C．四条边都相等的四边形是菱形；

D．顺次连接等腰梯形各边中点,得到一个矩形

答案

答案：D

考点：

分析：根据矩形、正方形、菱形、等腰梯形的判定即可求出答案．

解答：解：A、四边形的内角和为360°，正确；

B、对角线互相垂直平分且相等的四边形是正方形，正确；

C、四条边都相等的四边形是菱形，正确；

D、顺次连接一个四边形各边中点，得到一个菱形，那么这个四边形可能是矩形，不正确．

故选D．

点评：本题综合考查四边形的性质和特点．

问答题

什么是国有土地使用权挂牌出让
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单项选择题

Drug use is rising dramatically among the nation’ s youth after a decade of decline. From 1993 to 1994, marijuana use among young people (1) from 12 to 17 jumped 50 percent. One in five high school seniors (2) marijuana daily. Monitoring the Future, which (3) student drug use annually, reports that negative attitudes about drugs have declined for the fourth year in a row. (4) young people see great risk in using drugs. Mood-altering pharmaceutical drugs are (5) new popularity among young people. Ritalin, (6) as a diet pill in the 1970s and now used to (7) hyperactive children, has become a (8) drug on college campuses. A central nervous system (9) , Ritalin can cause strokes, hypertension, and seizures. Rohypnol, produced in Europe as a (10) tranquilizer, lowers inhibitions and suppresses short-term memory, which has led to some women being raped by men they are going out with. (11) taken with alcohol, its effects are greatly (12) . Rock singer Kurt Cobain collapsed from an (13) of Rohypnol and champagne a month before he committed (14) in 1994. In Florida and Texas, Rohypnol has become widely abused among teens, who see the drug as a less expensive (15) for marijuana and LSD. Alcohol and tobacco use is increasing among teenagers, (16) younger adolescents. Each year, more than one million teens become regular smokers, (17) they cannot legally purchase tobacco. By 12th grade, one in three students smokes. In 1995, one in five 14-year-olds reported smoking regularly, a 33 percent jump (18) 1991. Drinking among 14-year-olds climbed 50 percent from 1992 to 1994,and all teens reported substantial increases in (19) drinking. In 1995, one in five 10th graders reported having been drunk in the past 30 days. Two-thirds of high school seniors say they know a (20) with a drinking problem.

5（）

A.retaining

B.attaining

C.maintaining

D.gaining
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