（1)Is that your a book? 哪里错了your 和 a 不能同时使用改为：Is that your book?或：Is that a book?（2）This is a pen and that's a ruler? 应为肯定句,因此去掉问号.（3）Is this his pencil?此题正确!...不好意思 我打错了几个（2）This is a pen and that's a ruler.没有问号,但是有错的（3）Is this his pencil？————Yes,it's（2）This is a pen and that's a ruler.没有问号,但是有错的 修改为：This is a pen and that is a ruler.此为并列结构，is 最好缩写，或者都缩写（3）Is this his pencil？————Yes,it's应该为：Yes，it is. is不应缩写。