It's Complicated

The answer here is ultimately not important to my point. Rather, this question attempts to demonstrate the depth of knowledge needed to answer a question that most of us probably all know a little something about. For example, to correctly answer this question, you really need to know at least: 1) the order of succession, 2) what impact, if any, location has on succession, 3) what impact, if any, citizenship has on succession, and 4) what types of scenarios are covered by the Act.

Here, I think a lot of people might know right away that the third in line after the President and Vice President is the Speaker of the House. However, most people probably were a little put off by the fact that she was out of the country, and also wondered at the significance of her citizenship at birth. This answer is wrong if you realize that only national born citizens may hold the office of the President. So, no matter where the Speaker of the House is located, C cannot be the right answer.

The most easily eliminated choice is probably D, because you really only need to have a basic understanding of the Presidential Succession Act to know that it applies upon the death, incapacity, resignation or removal from office of the President.

If you really know the succession schedule well, you realized that the President pro tempore of the Senate is the next in line of succession, after the Speaker of the House is eliminated due to her citizenship. The President pro tempore's location, while curious, does not preclude her assuming the duties of the presidency, and is the best of the possible answers.

The Secretary of State is the next in line after the President pro tempore of the Senate. However, her ability to take office has nothing to do with the Secretary of the Treasury, because the Treasury Secretary is behind her in succession.