重点讲解：
1. a waste of
浪费；
eg. It is a waste of time to listen to his insignificant talk.
听他那些废话纯属浪费时间b(AZiGoPZE2fcTH]。
eg. I've finished with gambling it's a waste of money.
我已经戒赌了——赌博完全是浪费钱财SQ!bMyyn%Xi。
2. set off
点燃；
eg. If you drop a lighted cigarette, you could set off a fire.
如果你把一根点燃的香烟掉在地上，就有可能引起火灾A#noj3HZrdF。
eg. He likes to set off firecrackers during Diwali.
他喜欢在排灯节放鞭炮fV.(i[;[HZ3adAx;eQ0。
3. lead to
招致；致使；导致；
eg. There are recognised black spots in marriages which can lead to trouble.
婚姻中有一些公认的容易引发问题的雷区Ax+TABz!P=N%QMS)。
eg. Early success may lead to megalomania.
少年得志可能导致妄自尊大Q~2v#bJkJHygQ4Q。