This is a book.里“a”是什么词性?

This is a book I'd like to book a table tonight里的book是什么词性? Is this a book?" "Yes,this is." this is a book 提问 This is a interesting book This is (a math) book. This is s book.(a book提问) Is this a book?的复数形式是什么?3Q This is a book (对a 英语单词里a.是什么词性? This is a book.对a book进行提问 "this is a book" a book是宾语还是表语?