6.   If both the president and the vice president are unable to fulfill their duties, who takes over as president? 

A. President pro tempore of the Senate
B. Attorney general
C. Speaker of the House
D. Secretary of state

"In the case that the president can no longer serve, the vice president would serve as president."

Which one would I chose???

"If the vice president cannot serve, the line of succession falls to the speaker of the House, then to the Senate president pro tempore, then to Cabinet members."

http://www.cnn.com/2013/08/27/us/succession-presidential-and-vice-presidential-fast-facts/

I just looked on that site.

And what did you learn from that site?

If there is no vice-president, the line of succession falls to the next in order:

http://en.wikipedia.org/wiki/United_States_presidential_line_of_succession

Yes. C is right.

This happened several years ago. The vice president resigned and the Speaker of the House, Gerald Ford, became vice president. Then President Nixon resigned, and Ford became president.

Yes, C is correct, just as the quotation you posted says it is. And you question it?

Oh sorry for the ? at the end.

Gerald Ford was never Speaker of the House. He was appointed vice-president by President Nixon, but not because he was Speaker. He was the House Minority Leader.

Oops! Thanks for the correction, Reed.