Creating world peace is a rather difficult goal, ____ calls for efforts of many generations.

  A. one that   B. one  C. that  D. it

Creating world peace is a rather difficult goal, ____ calls for efforts of many generations.

1. A.
   one that
2. B.
   one
3. C.
   that
4. D.
   it

Creating world peace is a rather difficult goal, ____ calls for efforts of many generations.