A criminal case is an example of B. Prosecutorial Discretion. Criminal cases begin when a suspected criminal is indicted by a gran jury, or charged with the criminal offense by a prosecutor or district attorney. Prosecutors also exercise unfettered discretion adn they decide who they charge, on what charges and when they want to drop them or bargain.
The Missouri Bar Plan provides for selecting judges on the basis of C. Merit. Under the plan, a non-partisan commission reviews the merits of the candidates and sends a list of the best qualified candidates to the governor, who then has 2 months to select a candidate from the list.
The term one-shotter refers to B. Litigants who make only occasional recourse to the courts. These litigants, either a person or an organisation, tend to have few resources and do not frequently deal with the legal system.