Each chamber must approve the same bill before it can be sent to the president. In a majority of cases, the second chamber simply approves the one approved by the first, and it is presented to the president for signature. If there are differences, there are two options for compromise. Historically, most major bills are resolved in conference committee, though the two chambers may also exchange amendments, or both. For example, they might agree to immediately go to conference and then resolve any remaining differences with an amendment exchange. Or they may first attempt to exchange amendments and then decide to go to conference.