they are good student 和they are good students那句正确?还是都正确?

英语阅读题 100分There are four people in the twins’ family .They are the twins,their father and their mother.The twins’ names are Lucy and Lily.They are fourteen.They are in the same class in the NO.1 Middle School.They are very good studen they are good friends they are good of They are good for He is a good studen 怎么翻译? Are they good for us? They are us good friends What are they good at? they are good frends意思 they are good strict me They are good for me. are you a studen的单数形式 ( )are her students.They are good( )are her students.They are good students. They are in different classes,b( ) they are good friends. they are my good friends改否定 They are our good friends改为复数 They are good friends.改为否定句 when they are having a good