重點講解：
1. all of a sudden 突然地；出乎意料地；
例句：All of a sudden she didn't look sleepy any more.
她突然看起來一點都不困了=;08rJD)N#。
2. pay off 償清，還清（債務(wù)）；
例句：It would take him the rest of his life to pay off that loan.
他得用余生來還清那筆貸款!Aaj!G6TIU3gd;Wt-。
3. lead to 招致；致使；導(dǎo)致；
例句：A lack of prudence may lead to financial problems.
不夠謹(jǐn)慎可能會導(dǎo)致財政上出現(xiàn)問題V.!S9)1St[ldL4NWnuj。
4. be responsible for 負(fù)有責(zé)任的；應(yīng)承擔(dān)責(zé)任的；
例句：He could never quite put his finger on who or what was responsible for all this.
他一直就搞不清楚是誰或者什么造成了這一切5!38,g6UJ.Gl.。