选择题:根据以下材料,回答题People have smoked cigarettes for a longtime now. The tobacco whi...

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根据以下材料,回答题 People have smoked cigarettes for a longtime now. The tobacco which is used to make cigarettes was first grown in whatis now part of the United States. Christopher Columbus, who discovered America,saw the Indians smoking. Soon the dried leaves were transported to Europe. In thelate 1800s, the Turks made cigarettes popular. Cigarette smoke contains at least twoharmful substances, tar and nicotine. Tar, which forms as the tobacco burns,damages the lungs and therefore affects breathing. Nicotine, which is found inthe leaves, causes the heart to beat faster and increases the breathing rate.Nicotine in large can kill a person by stopping a person′s breathing muscles.Smokers usually take in small amounts that the body can quickly break down. Nicotine can make new smokers feel dizzy (头晕) or sick to theirstomachs. The heart rate for young smokers increases 2 to 3 beats per minute.Nicotine also lowers skin temperature and reduces blood flow in the legs andfeet. It plays an important role in increasing smokers′ risk of heart disease andstroke. Smoking cigarettes is dangerous. Cigarettesmoking was the cause of lung cancer and several other deadly diseases. What′s the main idea of this passage 查看材料

A.Where did cigarettes come from B.The effect of smoking on your body. C.How to smoke is healthy D.Who is the first smoker

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根据以下材料,回答题Sometimes I really doubt whether there islove between my parents....

根据以下材料,回答题Sometimes I really doubt whether there islove between my parents....

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既可以活血,又可以行气的药物是()A.川芎B.延胡索C.红花D.郁金E.桃仁

既可以活血,又可以行气的药物是()A.川芎B.延胡索C.红花D.郁金E.桃仁

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关于糙面内质网下列叙述错误的是()A.糙面内质网表面附着大量核糖体B.糙面内质网常与核膜相接C.糙面内质网是扁囊状内质网D.糙面内质网来自于

关于糙面内质网下列叙述错误的是()A.糙面内质网表面附着大量核糖体B.糙面内质网常与核膜相接C.糙面内质网是扁囊状内质网D.糙面内质网来自于光面内质网E.核糖体与糙面内质网结合属功能性结合

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f(x)=x2,则f′(x)在x=2处的导数值为__________。

f(x)=x2,则f′(x)在x=2处的导数值为__________。

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已知曲线y=ex与直线y=c(c>1)及Y轴所围成的平面图形的面积为1,求实数c的值。

已知曲线y=ex与直线y=c(c>1)及Y轴所围成的平面图形的面积为1,求实数c的值。

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