Final answer:
The Under Secretary of Defense is responsible for overseeing and developing harassment prevention and response program strategies and plans.
Step-by-step explanation:
Overseeing and developing harassment prevention and response program strategies and plans falls under the purview of: c. Under Secretary of Defense. The Under Secretary of Defense (USD) is a high-ranking official within the Department of Defense (DoD) and is responsible for various policy matters, including the development and oversight of programs related to harassment prevention and response. This role involves formulating strategic initiatives, coordinating efforts across the military branches, and ensuring compliance with relevant policies. While the Inspector General and the Secretary of Defense play crucial roles in oversight and leadership, the specific responsibility outlined—harassment prevention and response program strategies and plans—aligns more closely with the Under Secretary of Defense's portfolio.