1． be +at引导的介词短语

be at war正在交战

e.g. the two countries are at war now.

be at work 正在工作

e.g. Jim is at work on his car now.

be at peace 处于和平或平静状态

e.g. Thus Europe was at peace for the first time in ten years.

be at table 正在吃饭

e.g. when Iarrived, my friends were at table.

常见的这类结构有：be at meeting 正在开会；be at school 正在上学；be at breakfast (在吃早饭/午饭/晚饭)；be at church 正在做礼拜，等等。

2． be +in 引导的介词短语

be in progress 正在进展

e.g. the building of the bridge is in progress.

be in trade 正在做买卖

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

Be in fashion 流行

e.g. Long hair is very much in fashion now.

be in trouble 处于困境/困难之中

e.g. I am in great trouble. My little boy has fallen off a ladder and hurt himself.

常见的这类结构还有：be in danger 处于危险之中；be in operation 正在运行；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，等等。

3． be +on引导的介词短语

be on strike 正在罢工

e.g. the cleaners have been on strike for several weeks.

be on leave 正在休假

e.g. several soldiers are on leave in our village.

be on the rise 正在上涨

e.g. price of vegetables are on the rise.

常见的这类结构还有：be on a visit 正在访问；be on sale 正在出售/削价出售，等等。

4． be +under引导的介词短语

be under consideration 正在考虑之中

e.g. the plan is under consideration by the Ministry of Education.

be under construction 正在修建之中

e.g. the new railway is still under construction.

be under discussion 正在讨论之中

e.g. that issue has nothing to do with the matter under discussion.

常见的这类结构还有：be under treatment正在治疗之中，be under repair正在修理之中等等。