The correct answer is A) serving a committee.
The best method for a Senator to have power in making legislation is serving on a committee.
The Senator needs to be part of a Committee in Congress so he/she can have more power, influence, and express its ideas to be known by other Senators, congressmen, government officials, the Media, and the public.
The Senator can be part of these committees: Committee on Budget, Committee on Agriculture Nutrition and Forestry, Committee on Armed Service, Committee on Environment and Public Works, Committee on Foreign Relations, among many others.