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

---So have I.  

1. A.
   is reading
2. B.
   has read
3. C.
   reading
4. 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. 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