Politicians have a greater interest in serving the voters' will when:

a. the policy is highly visible.

b. voters are well informed.

c. the media does not get involved.

d. special interest groups are nonexistent.

a. the policy is highly visible.

Explanation:

Political parties formed programs and policies based on their election promises and their awareness about the discontent in the citizens. These policies would gather more support of the people towards them. When these policies are implemented effectively, it increases the credibility of the political parties in the eyes of voters.

Answer: a) the policy is highly visible.

Explanation:

Politician tend to perform maximum activities and works according to voter's will when the political plan is perceived by the voters clearly. They follow the policy because they are discovered by the voters in well known manner. If they don't follow the policy they might not receive votes next time or voters will disregard the politician.

Other options are incorrect because information persisting voters, media intervention and absence of special interest group are not the factors that influence political to perform activities as per voters's desire. Thus, the correct option is option (a)