U.S. antitrust enforcement policies have focused on
1) Enforcing market codes of ethics
2) Preventing "golden parachutes"
3) preventing price fixing arrangements
4) forcing firms to produce output at the point where P=MC
5) breaking up any firm with more than 10 Percent market share
Do a little research, then take a shot, what do you think?
Hint: Lots of firms today have a 10+ percent market share and a regulator knowing a firm's MC is quite a tall order. So there are two you can eliminate.