全国中学生英语能力竞赛的“句型转换”题主要有两大类：一是基本句式的转换；二是同义句的转换。我们今天只讨论基本句式的转换。
基本句式的转换主要是指“肯定句、否定句、一般疑问句、特殊疑问句、反意疑问句和选择疑问句、祈使句、感叹句”的转换。句式的转换一般都有一定的规律可循，我们就是要掌握它们的变化规律，能够举一反三，见此知彼。
一、肯定句、否定句和一般疑问句的转换
这三种句型的转换有共同的规律可循，有几个要点必须牢记。我们可以把各种句式归为两大类：1、含有be动词、助动词和情态动词的句子；2、只有行为动词的句子。
第1类句子，肯定句改为否定句时，一律在be动词、助动词和情态动词后加“not”。改为一般疑问句时，一律将be动词、助动词和情态动前移到句首（首字母大写）。肯定回答用“Yes”；否定回答用“No”。“Yes”或“No”后面的主语必须用代词，“No”后面必须用否定缩略式。如：
将下列句子改为否定句、一般疑问句，并做肯定、否定回答。
1．There are some computers in this school．（be动词）
There aren't any computers in this school．
Are there any computers in this school？（Yes，there are．／No，there aren't．）
2．Li Ming's father can drive a car．（情态动词）
Li Ming's father can't drive a car．
Can Li Ming's father drive a car？（Yes，hecan．／No，hecan't．）
3．She has already finished her homework now．（助动词）
She hasn't finished her homework yet．
Has she finished her homework yet？（Yes，she has．／No，she hasn't．）
第2类句子必须借助助动词do；does； did。改为否定句，在行为动词前加don't（一般现在时态，主语是除第三人称单数之外的人称和数时）；doesn't（一般现在时态，主语是第三人称单数时）；didn't（一般过去时态）。改为一般疑问句时，在句首加Do；Does或Did。肯定回答用“Yes”，后面动词用do；does或did”；否定回答用“No”，后面动词用don't；doesn't；didn't。如：
将下列句子改为否定句、一般疑问句，并做肯定、否定回答。
1．The children like playing games．
The children don't like playing games．
Do the children like playing games？（Yes， they do．／No，they don't．）
2．Mary usually goes to school on foot．
Mary doesn't usually go to school on foot．（原第三人称单数改为原形）
Does Mary usually go to school on foot？（Yes，she does．／No，she doesn't．）
3．Tom went to London yesterday．
Tom didn't go to London yesterday．（原过去式改为原形）
Did Tom go to London yesterday？（Yes，he did．／No，he didn't．）
