Meeting my uncle after all these years was an unforgettable moment, I will always

treasure_____.  

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

Meeting my uncle after all these years was an unforgettable moment, ____ I will always treasure.

　 A. that 　 B. one  C. it 　 D. what

Meeting my uncle after all these years was an unforgettable moment, _        I will always treasure．

Meeting my uncle after all these years was an unforgettable moment, _        I will always treasure．

Meeting my uncle after all these years was an unforgettable moment, _____ I will always treasure.