按照课文内容填空 （共8小题；每小题0.5分,满分4分）
阅读下面的短文,在标有序号的空白处填入一个适当的词,或填入括号中动词的适当形式。
It’s easy for you to start smoking, but  ___you become addicted to it, you may find it  ____to stop smoking. Firstly, you may become __ addicted to nicotine, one of the hundreds of harmful chemicals __(consist) in cigarettes. When the drug leaves your body, you get withdrawal symptoms. Secondly, you get addicted ____ habit. ___ is, if you do the same thing repeatedly, you begin to do it ____. Lastly, you become mentally addicted to it, when you may believe that you will only feel good when you smoke and may find all kinds of negative emotions in you when you stop smoking. Smoking may have all kinds of harmful effects on the health of both the smokers themselves and non-smokers around them. So it is time that smokers ____(quit) smoking.