--- Each of the students, working hard at their lessons, ______ the book.

    --- So have I.

    A. is reading       B. has read        C. reading       D. reads

— Each of the students, working hard at their lessons, ______the book.   

— So have I.

       A. is reading   B. has read     C. reading      D. reads

— Each of the students, working hard at their lessons, ______the book.  — So have I.

       A. is reading       B. has read          C. reading          D. reads

---Each of the students working hard at their lessons ________ the book.

  ---- So have I.

A.is reading    B. has read     C. read    D. reads

—Each of the students working hard at their lessons　　　　 the book.

—So have I.

A.is reading　　　　　 B.has read　　　　　 C.read　　　　　　 D.reads