【心中有数】
单元语法发散思维
一、介词形式，被动意义
This new railway is still under construction . 这条新铁路仍在建设中。
本句中的under construction “正在建设中”。介词under构成的短语，如果它的宾语是表示动作的名词，通常含有被动意义，意为“在……过程中”。它可改换为被动语态。但介词结构使句子言简意赅，避免过多地使用被动语态。这种介词短语在句中常作表语，也可作补足语或定语。例如：
Your suggestion is still under discussion . 你的建议正在讨论中。
He is said to be under arrest fr stealing . 据说他由于偷窃被捕了。
The house under repair is our classroom building . 正在修建的房屋是我们的教学楼。
常见的这类under短语还有：
under attack在进攻中，under arrest在关押中，under consideration在考虑中，under construction在建设中，under contact在联系中，under discussion在讨论中，under examination在审查中，under investigation在调查中，under repair在修理中，under review在审议中 under treatment在医治中，under trial在受审中
还有一些介词，如in , on , for , above , beyond , past , out of , within等，也可以构成表示动作的介词短语。如：
The writer has finished writing his novel but it is not yet in print . (= …being printed)
作者已经写完了他的小说，但尚未出版。
Grapes from XinJiang are on sale . (=…to be rented) 还有两间房出租。
His virtue is above all praise . (=…can’t be praised completely) 他的美德赞颂不尽。
The fellow’s insolence is beyond endurance . (=…can’t be endured) 这家伙傲慢无礼，叫人受不了。
His car was out of control . (=…could not be controlled)那部汽车失去了控制。
The pain was almost past bearing . (=…couldn’t be borne) 痛得简直受不了。
The city is already within sight . (=…can be seen already) 城市已经望得见了。(在视野之中)
二、主动形式被动意义
初学被动语态不少同学常将应该用主动形式的句子错用为被动形式。请看如下句子和两
道高考题：
1. Those programmes are usually easy to receive and not difficult to understand .
2. They were still difficult to read and were very heavy to carry .
3. The sick woman needs ______ ( MET88 – 2 )
A . Looking after B . to be looking after
C . to look after D . being looked after (A)
4. We think the film is ______ ( MET85 – 1 )
A . worth to see B . worthy of seeing
C . worth seeing D . worthy to see I
句1意思为：这些节目通常很容易接收到而且也不难理解。句2意思为：这些书籍读起来还是很费劲，拿起来又很重。在学习句1句2时，学生习惯误译为：1. Those programmes are usually easy to be received and not difficult to be understood . 2. They were still difficult to be read and were very heavy to be carried . 所以总结一下主动形式表被动意义的情况是十分必要的。
(一) 不定式主动形式表被动意义
1 . 当不定式用在作表语的形容词后，在句中作状语，而句中的主语又是不定式的逻辑宾语时，通常用不定式主动形式表示被动意义。如上述句1句2。能带主动语态的不定式而表达被动意义的形容词常见的有：easy、difficult、heavy、hard、nice、bitter、dangerous、light、interesting、important、expensive、fit、comfortable、pleasant、impossible等。其句型为S + link v + adj . + infinitive ( 主动语态 ) ，类似这种貌似主动实为被动的系表结构的又如以下例句。