They have made so great progress      .

                A. three years ago                                             B. for three years

                C. in the past three years                                D. before three years

They have made so great progress      .

                A. three years ago                                             B. for three years

                C. in the past three years                                D. before three years

They have made so great progress      .

They have made so great progress      

1. A.
   three years ago
2. B.
   for three years
3. C.
   in the past three years
4. D.
   before three years