我们先来看一道考题：

Only in this way __________ able to finish the work in time.

A. can you be                         B. are you                         C. you can be                        D. you are

此题应选 B。容易误选D。至于A，C，这比较容易排除，因为情态动词 can 不能与 be able to用在同一谓语中。本题之所以要选B而不选D，主要是因为句首用了only in this way 的缘故，按照英语语法规则：“only+状语”位于句首，句子通常要用倒装语序(部分倒装——用一般疑问句形式)：

1. “only+副词”位于句首：

Only then did I realize that I was wrong. 只是到了那时我才意识到是我错了。

Only by shouting was he able to make himself heard.  他只有叫喊才能让别人听到他。

The pilot reassured the passengers. Only then did I realize how dangerous the situation had been. 飞机驾驶员要乘客们放心，这时我才明白刚才的情况有多危险。

2. “only+介词短语”位于句首：

Only by working hard can you succeed. 只有努力工作你才能成功。

Only in the reading-room can you find him. 你只有在阅览室才能找到他。

3. “only+状语从句”位于句首：

Only after she died was I able to appreciate her. 只有到她死后我才认识到她的价值。

Only when one loses freedom does one know its value. 一个人只有在失去自由后才知道自由的可贵。

注意：

若位于句首的不是only+状语，而是 only+宾语等，则通常无需倒装(但有时也可以倒装)：

Only a policeman the children saw in the street. 孩子们在街上只看到一个警察。

Only one more point will I make. 我只再说明一点。

only后跟的是主语，就不用倒装结构了。 
Only when the war was over in 1918 was he able to get back to work．(倒装句）
Only five men were hurt in the accident．（不倒装）