Two persons are discussing something at a party. A third person, a common acquaintance of both joins them. The third person should

A

Inquire about the discussions being held prior to his arrival.

B

Greet them and start a new topic of discussion.

C

Greet them, feel sorry that he disturbed them and leave the scene.

D

Greet them, feel sorry that he disturbed them and seek permission to join the discussion.