Hi,Joe!What (a )you reading?I'm reading an (i )book.Raelly?W

Hi,Joe!What (a )you reading?I'm reading an (i )book.Raelly?W M:Hi,Bill.What are you ()?B:I'm reading a report on Chin I'm reading an i_____ book . I'm reading an English book --------China. what are you doing?i'm reading a book by Mark Twain.A.writte -_____?-I'm reading a book.A.What about you B.Really C.Why n I‘m reading an English book（对reading an English book提问） I am reading an (i ) book A:Hi,Li Lei.What are you (1)____________?B:I am reading a le I am reading a book I'm reading a book.划线提问,如果划了reading a book,应该怎么问? I'm reading a book .中的主语,谓语,宾语是什么?