Senatorial courtesy:

A. gives a senator a role in appointing judges.
B. means that questioning judicial nominees follows committee seniority.
C. played a role in confirming judges in the nineteenth century but is no longer practiced.
D. refers to senators not criticizing one another during floor proceedings.

A?

Senatorial Courtesy is a custom whereby presidential appointments are confirmed only if there is no objection to them by the senators from the appointee's state, especially from the senior senator of the president's party from that state.

From your choices, which best would explain this?

http://www.thefreedictionary.com/senatorial+courtesy

Senatorial courtesy refers to the practice where the President of the United States consults with senators from a nominee's home state before officially nominating a candidate for a federal judgeship. This tradition is based on the principle that senators from a particular state have valuable insights about the qualifications and suitability of potential judges for their state.

The correct answer to your question is:

A. Senatorial courtesy gives a senator a role in appointing judges.