People have smoked cigarettes for a long time now. The tobacco which is used to make cigarettes was first grown in what is now part of the United States. Christopher Columbus, who discovered America, saw the Indians smoking. Soon the dried leaves were transported to Europe. In the late 1800s, the Turks made cigarettes popular.
Cigarette smoke contains at least two harmful substances, tar and nicotine. Tar, which forms as the tobacco bums, damages the lungs and therefore affects breathing. Nicotine, which is found in the 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 their stomachs. 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 and feet. It plays an important role in increasing smokers′ risk of heart disease and stroke.
Smoking cigarettes is dangerous. Cigarette smoking was the cause of lung cancer and several other deadly diseases.
___________ doesn′ t make one′ s heart beat as usual.
细节题。根据第二段第三句“Nicotine，which is found in the leaves，causes the heart to beat faster and increases the breathing rate．”可知答案为B。
我国保护少年儿童权益的专项法律是《中华人民共和国未成年人保护法》。（ ）
MP3（ ）。
计算机软件是指（ ）。
下面哪一项不属于维护交易安全原则的内容？（ ）
围绕《建国以来的重大科技成就》一课，做一个教案。
请围绕“城乡发展一体化”写一篇小论文，题目自拟，角度不限，要求：结构完善、条理清晰、有说服力。
在国际关系中，第三世界国家历来是中国团结合作的对象，因为 ①第三世界国家是国际社会一支重要的政治力量 ②团结第三世界国家符合中国的国家利益 ③合作是第三世界国家共同发展的必由之路 ④第三世界国家在南北关系中处于主导地位（ ）
微观经济学要解决的问题是（ ）
机关文书部门或业务部门在年终或第二年上半年对归卷的文件材料进行整理等工作，称为（ ）。
20世纪70年代中国外交有了重大突破和转机，转变的关键是（ ）
