Last month, American scientists started working on _____ project aimed at improving _______ ability to predict earthquake.

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

Last month, American scientists started working on _____ project aimed at improving _______ ability to predict earthquake.

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

Last month, American scientists started working on _____ project aimed at improving _______ ability to predict earthquake.

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

Last month, American scientists started working on _____ project aimed at improving _______ ability to predict earthquake.