One of the most important nonlegislative functions of Congress is the power to investigate. This power is usually delegated to committees, either the standing committees, special committees set up for a specific purpose, or joint committees composed of members of both houses. investigations, commonly held in the form of Investigatory hearings, are conducted to gather information for the following three main reasons: (1) to consider pending legislation, (2) to investigate issues that may require legislation in the future, and (3) to investigate and oversee federal programs.
Bearing this in mind, it could be said that the option A. to oversee executive agencies, could be a reason why Congress would issue its power to investigate.