The best answer to the question above would be the second sentence. The phrase 'Our mission continues' supports the central idea of the speech which is that America's ongoing fight with the terrorists Al-Qaeda will be one that the country will not easily abandon. Other choices are not the main points.
Hey :)
I'm not exactly sure of the answer, but I think it's "to remind the reader that war is unavoidable"
Sorry if it's incorrect >-<
Hope this helps!!!!
