The correct answer is: None of them.
The Mahabharata does not mention that the ‘Kulinda’ people were conquered by any of the three rulers listed in the question. In fact, the Mahabharata does not mention the ‘Kulinda’ people at all.
The ‘Kulinda’ people are mentioned in the Puranas, which are a collection of ancient Hindu texts. According to the Puranas, the ‘Kulinda’ people were a tribe that lived in the Himalayas. They were said to be a fierce and warlike people.
The Puranas also mention that the ‘Kulinda’ people were conquered by the Pandavas, the heroes of the Mahabharata. However, this story is not found in the Mahabharata itself.
It is possible that the story of the ‘Kulinda’ people being conquered by the Pandavas was added to the Puranas later, after the Mahabharata was written. It is also possible that the story is simply apocryphal.
In any case, there is no evidence that the ‘Kulinda’ people were ever conquered by Arjuna, Smudragupta, or Asoka.