Coming across an old friend I had never seen for years on the top of Mount Tai was really an amazing moment, ________ reminding me of many old good days we’d spent together．

1. A.
   what
2. B.
   which
3. C.
   one
4. D.
   that

Coming across an old friend I had never seen for years on the top of Mount Tai was really an amazing moment, ________reminding me of many old good days we’d spent together.

A. what                        B. which                      C. one                                 D. that