2. Vile indeed, but habit-forming and therefore lethally dangerous: it cuts short the lives of between a third and half of its practitioners. 吸烟有百害而无一利,但却容易成瘾,因此危害是致命的:吸烟者中三分之一到一半的人寿命缩短。
3. Within a few days, the animals are hooked: they readily self-administer cocaine, heroin, amphetamine and many other common habit-forming drugs. 几天之后动物就上瘾了,牠们轻易地为自己注射古柯碱、海洛因、安非他命,以及其他许多常见的成瘾药物。