英語問題：把下列句子改錯！ 我要所有答案，並給我說說是怎樣改錯的！！！緊急！！！

1.We have been in China for three years . for+時間段，壹般用於完成時 ago 壹般+時間點 壹般過去時

2.I bought the book a week ago for+時間段，壹般用於完成時 ago 壹般+時間點 壹般過去時

bought是瞬間動詞

3.Where have you been, Jane? have been to去了回來了 have gone to 去了未回來 根據題意 have been to去了回來了

4.You ought not to throw it.about 代詞放在動詞和介詞中間

5.It's known that Mingming does well in math. be good at / do well in