1. I think she is there.

　　误：I think she isn’t there.

　　正：I don’t think she is there.

　　析：英语中think, believe, expect, suppose等表示信念和揣测的动词，后接that从句时，习惯上将从句中的否定形式转移到主句上，即否定主句谓语，不否定从句谓语。

　　2. He can sing this song and that one.

　　误：He cannot sing this song and that one.

　　正；He cannot sing this song or that one.

　　析：肯定句中的连词and在否定句中一般要改为or。

　　3. Tom went to school too.

　　误：Tom didn’t go to school too.

　　正：Tom didn’t go to school either.

　　析：too和also用于肯定句中时，否定句中用either替换。