英文句子結構的變化(倒裝)

Inverted sentences
1) When you see " an adverb of frequency" , for example, " not often" in a sentence, you may change it to an inverted sentence by placing " Seldom, Rarely, or Hardly ever" in the front.
Example:
-They don't watch TV often.
- Seldom do they watch TV.<--------- inverted
2) If there is no helping verb in a sentence, a helping verb is needed in
an inverted sentence.
- John not only lost his job, but also got cheated by Mr. Lee.
- Not only did he lose his job, but also got cheated by Mr. Lee.( did = helping verb)
3) When you see sentences in the nagative
- My father didn't tell a single person his problems. ( didn't = negative)
- Not a single person did my father tell his problems.
- She has never kissed a man before. ( never = negative)
- Never before has she kissed a man.
4) When the word" when" appears in a sentence
- Helen understood how to write inverted sentences when she had finished the English class.
- Only when she had finished the English class did Helen understand how to write inverted sentences. ( inverted)
5) When you see words like " had"," did"," would" in a sentence
- They had read that book only once before.
- Only once before had they read that book. ( inverted)
Here is a link for you
http://www.englishpage.com/forums/archive/index.php/t-5032.html