Which of the following individuals served as Secretary of State?

Hillary Clinton served as Secretary of State from 2009 to 2013 under President Barack Obama. In this role, she was responsible for overseeing U.S. foreign policy, conducting diplomacy with other nations, and representing American interests abroad. Her tenure is notable for her involvement in significant global issues, including the U.S. response to the Arab Spring and the emphasis on women's rights internationally.

Timothy Geithner served as Treasury Secretary, not Secretary of State, focusing on economic and financial matters. Leon Panetta held the position of Secretary of Defense and was involved in military and defense issues. Jason Chaffetz is known for his role as a U.S. Representative and did not serve in the Cabinet or as Secretary of State. Understanding these distinctions highlights why Hillary Clinton is the correct choice for this question.