—What do you think of the grammar book?

—Oh,it really is        useful reference book,which is worth reading        second time.

A.a;a                            B.an;the                       C.an;a                          D.the;the

---What do you think of the grammar book?

---Oh, it really is _________ useful reference book, which is worth reading _________ second time．

1. A.
   a; a
2. B.
   an; the
3. C.
   an; a
4. D.
   the; the

---  What do you think of the grammar book?.

  ---  Oh, it really is _______useful reference book, which is worth reading _______second time.

A. a; a    B. an; the      C. an; a     D. the; the

—What do you think of the grammar book?

—Oh, it really is_______ useful reference book, which is worth reading_______ second time.

A. a; a　　　　　　 B. an; the　　　　　　　　　　　　　　    C. an; a　　　　   D. the; the