介词ON的常见用法
on的用法比较重要，本文介绍它的一些常见用法：
1.动词+on
a)动词+ on要认真区分下面一些词组
act on对…有作用, bring on促使；导致, call on拜访某人,count on依赖, carry on执行,depend on取决, feed on以…为生,figure on料想；推断, go on继续,have on穿着, insist on坚持,keep on继续, lean on依赖, live on以…为生, pull on迅速穿上,put on穿上, switch on接通（电源）, take to喜欢；养成；轻易学会，turn on接通（电源）, work on操作, wait on侍候。
b)动词+sb.(sth.)+ on +sb.(sth.)
base on以…为基础, congratulate on恭贺, fix on固定, have mercy on怜悯,have pity on怜惜, keep watch on监视, spend on把时间、精力花在某方面。
2.be+形容词+on的词组
be dependent on依赖, be hard on对某人苛刻,be impressed on对…印象深刻, be keen on渴望, be strict on对…严格。
3.on+名词构成的词组
on board乘（车,飞机）,on call听候召唤, on duty值班, on earth到底, on fire着火, on foot步行，on guard在岗，on hire雇用，on holiday度假
介词IN的常见用法
1.动词+in
a)动词+ in
believe in信任, break in碎成，bring in引起；产生；带来, call in下令收回, fill in填充,get in收获, hand in上缴, involve in涉及, lie in在于, result in导致, share in共享,succeed in成功, take in卷起；订阅, turn in归还当局。
b)动词+sb./time/money+ in
help sb. in帮助某人做某事, spare time/money in匀出时间或钱做某事,spend time/money in花时间或钱做某事,waste time/money in浪费时间或钱做某事。
2. be +形容词+ in
be active in活跃于,be absorbed in专心致志, be busy in忙碌, be born in出生于,be concerned in牵涉, be clothed in穿着, be disappointed in对…失望,be diligent in勤于, be experienced in在…有经验, be employed in任职于,be engaged in忙碌, be expert in某方面的专家, be excellent in在…优秀,be interested in对…有兴趣, be lacking in缺乏, be rich in富有,be slow in迟缓, be successful in在某方面成功, be skilled in精于,be strict in严于, be weak in弱于。
3. in +名词
in advance提前,in all总共，in balance总而言之，in bed卧床，in body亲自，in brief简明扼要，in case万一, in charge主管，in danger有危险, in debt负债, in despair失望,in force大量地；有效，in full全部地, in flower开花,in general一般说来,in itself本身, in love恋爱, in order井然有序, in person亲自,in public公开地, in progress有进展, in practice从实践上看, in rags穿着破衣,in research探索, in return作为报答,in ruins一片废墟,in short总之,in theory从理论上看, in trouble有麻烦, in tears眼泪汪汪,in time及时, in turn按顺序, in vain白白地，in view看得见。
AT的常见用法 at构成的词组比较多，要细心区分。
1.动词+ at
arrive at抵达,call at访问某地, catch at(it)当场抓住, come at攻击, fire at向…开火,glance at瞟一眼, glare at怒目而视, grieve at忧伤，knock at敲,laugh at嘲笑, look at看一眼, pull at拉扯, rejoice at对…高兴，smile at向某人微笑, shoot at朝…射击, stare at怒目而视,thrust at刺向, tear at撕, tremble at颤抖，wonder at吃惊，work at工作。
2. be +形容词/过去分词+ at
be angry at恼怒于, be alarmed at对…保持警觉,be astonished at对…吃惊, be bad at不擅长, be clever at对某事很灵巧,be delighted at高兴，be disgusted at厌恶, be disappointed at对…失望，be good at擅长, be impatient at对…不够耐心, be mad at狂热于,be pleased at对…感到高兴, be present at出席, be satisfied at满意,be surprised at吃惊, be shocked at对…非常震惊，be terrified at受到…的恐吓,be quick at对…很机敏。
3.at+名词构成的词组
at a distance在一定距离，at a loss不知所措， at a time一次，at all一点也不，at any cost不惜一切代价，at best最好也只是，at first起初，at hand手头，at heart在内心里，at home在家；无拘束，at last最后，at least至少，at most最多，at once马上，at present目前。