16.People have smoked cigarettes for a long time now.The tobacco used to make cigarettes was grown in what is now part of the United States.Christopher Columbus,who discovered America,saw the Indians smoking,and soon the dried leaves were transported (運(yùn)輸) to Europe where smoking began to catch on.In the late 1800s,the Turks (土耳其人) made cigarettes popular.
Cigarettes smoke contains at least two harmful substances (物質(zhì)),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 breathing rate.
Smoking cigarettes is dangerous.The U.S.Public Health Service stated that cigarette smoking is the cause of lung cancers and several other deadly diseases.The U.S.government now requires that each package of cigarettes bear (帶有) a special warning about the danger of smoking.
16.The expression"catch on"in the passage may meanC.
A.start
B.cost a lot
C.become popular
D.dangerous
17.Before Columbus discovered AmericaD.
A.Europeans had smoked
B.Nobody smoked in the world
C.Nicotine was not in tobacco
D.Europeans had never smoked
18.In the nineteenth century smoking became popular because of the people inB.
A.India
B.Turkey
C.the U.S.
D.British
19.Breathing is affected byD.
A.nicotine B.Tar
C.heat D.both A and B
20.Which of the following is Not right?B
A.Smoking cigarettes is thought to be dangerous.
B.The U.S.Public Health Service has found the cause of lung cancers and several other deadly diseases.
C.Cigarette smoking is the cause of lung cancers and several other deadly diseases.
D.The U.S.government wants smokers to know the danger of smoking.