Appreciable adverse effect on competition triggers a statement of objections and structured opportunity for parties to propose modifications. When the Commission considers a combination will have an appreciable adverse effect on competition it issues a statement of objections requiring parties to explain why the combination should be allowed and permits parties to submit modification offers. If a proposed modification is not accepted, the Commission must communicate insufficiencies and call for revised proposals, evaluate such revisions within the prescribed period, and may itself propose modifications for parties' consideration.