This book is a favorite with students分析下这个句子的句型.看不懂为什么里面用a?

This is a book a favor of this service ,is a favor of recent origin 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)