Is collusion legal in the United States? If so, under what conditions is it possible when firms interact repeatedly? Is collusion more likely in industries with a large number of firms? Please choose the correct option from the provided answers.
1) Yes, collusion is legal in the United States.
2) No, collusion is not legal in the United States.
3) Collusion is only legal under certain conditions when firms interact repeatedly.
4) Collusion is more likely in industries with a large number of firms.