he needs some paper to write on 为什么要填write on啊
问题描述：
he needs some paper to write on 为什么要填write on啊
答
是写在纸上面 不是写纸 所以要加介词on
答
因为我们要用不定式做定语，放在被修饰词的后面，但是被修饰词要与不定式有主谓，动宾关系，如i need some books to read,water to drink / a person to share my happiness and sorrow等,这是动宾关系，和主谓关系，read the book,drink the water,the person shares my happiness
但是如果一些不及物东词不能构成动宾关系，需要介词帮助，如i need a room to live in/ i need a friend to talk with .
所以i need paper to write on/ i need a pen to wrtie with
答
write on 写,记述；在…上写
write on some paper 写在纸上