The idea that elected representatives should listen to their constituents' opinions and then use their best judgment to make decisions is called behaving as a

Trustee.

Explanation:

This can be seen to be a form of entrusting a democratic right to a person by a constituency in form of representing them. A trustee is seen to posses a high standard of integrity, honesty and loyalty etc as the case may seem to be. They are also seen to posses a form of selflessness where they are seen to put the interest of who they are representing first before their own priorities. In a bid to have performed exclusively well, they can be seen to be also entrusted with funds that are raised or required for charity and other selfless innovations with them as part of the head or totally heading the movement as the case may be.

the answer is d.index