介词 + 名词

　　在新概念第三册第14课有这么一句话：Whenever the Italian city-states were at war with each other, Hawkwood used to hire his soldiers to princes who were willing to pay the high price he demanded. 这里面有个非常好的仿写句型，就是用in+名词代替了进行时。如：i am having a class now.(我正在上课。)但"正在进行"这一动作，还可以用"be+介词短语"来表示。常见的介词短语类型有： be +at引导的介词短语;be +in引导的介词短语;be +on引导的介词短语; be +under引导的介词短语等。

　　ⅰ.be+at引导的介词短语 be at war(正在交战)：

　　the two countries are at war now.两国正在交战。

　　 (相当于：the two countries are waging a war now.)

　　be at work(正在工作)：jim is at work on his car now.吉姆正在修自己的车。

　　(相当于：jim is repairing his car now.)

　　be at peace(处于和平或平静状态)：

　　thus europe was at peace for the first time in ten years.

　　于是欧洲在十年以后第一次进入和平状态。

　　be at table(正在吃饭)：when i arrived my friends were already at table.

　　当我到达时，我的朋友们正在吃饭。

　　常见的这类结构还有：be at meeting正在开会;be at school正在上学;be at breakfast(lunch /supper)正在吃早(午/晚)饭;be at church正在做礼拜，等等。

　　ⅱ.be+in引导的介词短语 be in progress(正在进展)：

　　the building of the bridge is in progress.

　　这座桥梁正在施工中。(相当于：the bridge is being built now.)

　　be in trade(正在做买卖)：

　　some people of this country are in gold and ivory trade.

　　这个国家的有些人正在做黄金和象牙买卖。 be in fashion(流行)：

　　long hair is very much in fashion now.如今，留长发正时兴。

　　be in trouble(处于困境/困难之中)：i am in great trouble.my little boy has fallen off a ladder and hurt himself.我遇上点麻烦，我的小儿子从梯子上掉下来，并且摔伤了。

　　常见的这类结构还有：be in danger处在危险中;be in operation正在运行; be in action在活动(运转/战斗)中;be in peril在危险之中;be in class正在上课;be in hospital正在住院;be in office在执政;be in tears正在流泪;be in milk正在产奶;be in issue正在争论之中;be in church正在做礼拜;等等。

　　ⅲ.be+on引导的介词短语

　　be on strike(正在罢工)：the electricity workers have been on strike for several weeks now.电力工人到目前已经罢工好几个星期了。(即现在仍在罢工)

　　be on leave(正在休假)：several soldiers are on leave in our village.几位军人正在我们村子里休假。

　　be on the rise(正在上涨)：prices of vegetables are on the rise.蔬菜价格正在上涨。

　　常见的这类结构还有：be on a visit正在访问;be on the stumps处在困难之中;be on sale正在出售(美语作：削价出售)，等等。

　　ⅳ.be +under引导的介词短语

　　be under consideration(正在考虑之中)：the plan is under consideration by the ministry of education.教育部正在考虑这项计划。

　　be +under construction(正在修建中)：the new railway is still under construction.新铁路仍在修筑之中。

　　be +under discussion(正在讨论之中)：that issue has no relation to the matter under discussion.那个问题和正在讨论的事没有关系。

　　常见的这类结构还有：be under treatment正在治疗中;be under repair正在修理中，等等。

　　值得英语学习者注意的是

　　⑴尽管be+介词短语能表示"正在进行"这一意义，但它和be+现在分词所表示的语法意义是有差别的。前者着重事物所处的状态，偏重于静态;后者着重事物的动态，集中表示事物的动感。

　　⑵绝大部分这类结构，其名词前都没有冠词，假如加一冠词，意义将大相径庭。如：The Conservative Party is in office.保守党在执政。The principal is now in the office.校长现在在办公室。英语学习者对上述差别决不可掉以轻心。