Electronic cigarettes started out being marketed to smokers as a way to help them quit. Now e­cigarettes have been mainstreamed.Scientists expect to see more information coming out about e­cigarettes and their health effects.

　　E­cigarettes don't fill the lungs with harmful smoke，but that doesn't make them a healthy alternative to regular cigarettes.When you use an e­cigarette，you're still putting nicotine—which is absorbed through your lungs—into your system. In addition to being an addictive drug，researchers at the University of Utah used some animals to conduct a study to prove the toxic effects of nicotine.Later it was once even used as a chemical drug to kill some insects in agriculture.

　　Nicotine affects your brain，nervous system，and heart.It raises the blood pressure and the heart rate. The larger an amount of nicotine，the more a person's blood pressure and heart rate go up.This can cause an arrhythmia(心律失常)．In rare casesely again.Over time，nicotine use can lead to serious medical problems，including heart disease，blood clots，and stomach diseases.

　　1．The underlined word“toxic”in Paragraph 5 is closest in meaning to________．B．poisonous ficial

　　D．curableout to be practical for smokers.

　　D．Because it is convenient for smokers to carry.

　　3．When using an e­cigarette，________．otine into lungs

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