this is a book (refer to ) the life in south africarefering to为什么?怎么不是refered to?which refer to可不可以?这里完全不明白,refering to 在这里做什么什么成分,

This is a book Is this a book? Yes,this is. This is s book.(a book提问) This is a book答语 This is a book.对a book进行提问 This is a book 改为复数句 This is a interesting book.找错误! this is a book改为复数形式 This a book is good 怎么改错 Is this a book?的复数句 改错题：This is a my book. This is a book变成一般疑问句 this is a nice book的感叹句? This is a nice book,____it?填空 改错This is a expensive book This is a book.(It's,Its) this is a book on ________(electronic) This is a Engilsh book.改病句