All of the following are examples of indirect strategies used by interest groups to advance their cause EXCEPT: a. Buttonholing.
b. Use of citizen grassroots lobbyists.
c. Electioneering.
d. Protests and civil disobedience.
e. Endorsements and ratings.

a. Buttonholing.

Explanation:

Buttonhole can be defined as stopping an individual so as he or she can listen to you. Buttonholing can simply be defines as the act of keeping an individual against his or her will so that he or she can listen to what you have to say. interest group are group or an association  of people who have similar interest, ides, aim  and pursue a common goal. interest group have different ways of which there communicate their interest of which buttonhole is not among them.

Indirect strategies are those ways or means that are not legal or straightforward that are used to achieve ones aim e;g civil disobedience. interest group will not hold an individual hostage so as to advance their cause or aim.