1.Teenagers under18 are not allowed to smoke,or they should be fined.为什么用or?2.They can set an example to their children.什么意思?我为什么看到了to换成for的?set an example to不是固定搭配吗?怎回事啊?set an example to sb.不是固定搭配吗?怎回事啊?