填空题
Most smokers want to stop smoke. Many of 77. ______ them have tried more than once but failed. 78.______ Although they know smoking may kill them and 79.______ cause a serious illness yet they can give it up. 80.______ The reason to it is that tobacco contains nicotine 81.______ that is a drug which gets one into habit of smoking. 82.______ Because you start taking the drug, it is hard to stop. 83.______ If you go without it for an hour or two, it 84.______ begin to feel bad. The only thing can stop85.______ you feeling bad is the drug containing in cigarettes. 86.______