進行形の文
進行形　 be + 〜ing　  〜しているところだ

   ＜現在進行形＞ 　  You  are  reading  Tom's  book.
                 Are  you       reading  Tom's  book?
     Whose book  are  you       reading?


   ＜過去進行形＞       You  were  reading  three  books.
                  Were  you        reading  three  books?
  How many books  were  you        reading?