Which representative votes according to the preferences of their constituency?

A representative who votes according to the preferences of their constituency is known as a delegate. This approach emphasizes the importance of the elected official adhering closely to the views and wishes of those they represent, reflecting the democratic principle of representing the electorate's interests. Delegates are expected to prioritize the opinions and desires of their constituents over their own personal beliefs or judgments when making decisions.

In contrast, a trustee operates on the principle that they are elected to use their own judgment to make decisions for the good of their constituency, even if those decisions may not align with the immediate preferences of the voters. An agency representative acts in a capacity that reflects the interests of particular groups or constituencies, but this role can incorporate elements of both delegate and trustee theories depending on the context. An incumbent, while being a current officeholder, does not inherently imply a specific voting style or approach to representing constituents. Therefore, the correct response highlights the role of the delegate in voting according to the preferences of their constituents.