据观察，三字一体的片语动词中，含“on”的相当多。请看下面这段新闻中就有一个常用的含“on”的三字一体片语动词：

　　The press yesterday quoted the President of the ruling party as saying that failure to crack down on corruption would give the impression that “certain powers were being used to protect it”. （严禁；严加取缔）

　　下面这些也是常见常用的，不妨学而用之：

　　● cash in on：谋取利益
　　“Let's cash in on the fine weather by playing some outdoor games we like.”

　　● break in on/ burst in on：干扰
　　“The loud noise of the quarrel between the two neighbours broke in on children's sleep.”

　　● zero in on：对准目标
　　“The members of the Opposition Party zeroed in on the government's new bill.”

　　● clamp down on：施加压力；取缔
　　“The government has decided to clamp down on all forms of illegal gambling.”

　　● read up on：熟读
　　“You need to read up on all the traffic codes before you learn driving.”

　　● brush up on：复习
　　“Before the examination, remember to sort out the lecture notes to brush up on all the important points.”

　　● check up on：检查
　　“The manager asked the secretary to check up on all the documents before posting them.”

　　● bear down on：袭击
　　“The soldiers are determined to bear down on the enemy's headquarters.

　　● close in on：逼近
　　“The people in the whole town were trapped when the enemy's army closed in on them.”

　　● come down on：坚决要求；处罚
　　“The bank came down on its debtors for immediate payment./ Our court is going to come down more severely on illegal immigrants.”

　　● get in on：分享；参与
　　“Betty was amazed because her good friends did not invite her to get in on the profitable enterprise.”

　　● creep up on：慢慢来；包围
　　“We hardly notice the way old age creeps up on us./ Doubt crept up on me about Tommy's trustworthiness.”

　　● cut down on：减少；削减
　　“More and more countries have promised to cut down on their military expenses.”

　　● crowd in on：包围
　　“The students crowded in on their teacher to ask her about their examination results.”

　　● fall back on：求助于
　　“He has spent all his savings and now has nothing to fall back on.”

　　● chuck away on：浪费
　　“Why did you have your advice chucked away on such a recalcitrant person?”

　　● hurl away on：浪费
　　“I don't know what will come of you if you go on hurling away on your hard-earned money.”

　　● borne in on：被人相信不疑
　　“Bit by bit it was borne in on the people that political critics had been hostile towards the country.”

　　● clean up on：击败；胜过
　　“The strongest fighter cleaned up on all his opponents.”

　　● sit in on：旁听
　　“Members of the public are allowed to sit in on some public lectures.”