The majority party constitute the group within the Senate that has the most power over what legislation is put on the agenda and whether it is passed. Option B is correct.
Members of the majority party generally decide the most significant questions presented to Congress. In addiion to this, members of the majority party also primarily control what will be considered by their chambers on a daily basis.
In the Senate, whoever has the majority will likely get more bills passed because they will garner more votes.
