重点讲解：
1. clean up
清理，清除；
eg. The mayor is determined to clean up the city.
市长决心清除市内的不良现象。
eg. They fought bravely to clean up the bandits.
他们英勇作战以肃清土匪。
2. participate in
参与；参加；
eg. I am too clumsy of speech to participate in the debate.
我太笨嘴拙舌了，参加不了辩论会。
eg. He tamed the urge to participate in the new venture.
他抑制住想参加新的冒险的冲动。
3. for the first time
初次；首次；
eg. He felt for the first time a stabof fear.
他第一次感到了一阵恐怖。
eg. I went to the tropics for the first time last year.
我去年第一次去了热带地区。
