Answer:
The correct answer to the question: How does the sentence "Our mission continues" support the central idea of the speech?, would actually be: It supports the main point that this is an ongoing fight that America will not abandon.
Step-by-step explanation:
Throughout the speech given by President George W. Bush, as the members of the USS Abraham Lincoln return to the U.S after having been deployed in Afghanistan, the idea that the war on terror is ongoing, even if these soldiers are returning home, as it is only fair, is the main one. President Bush, through the use of such a phrase as "Our mission continues", and "Al-Qaeda is wounded, not destroyed", "The enemies of freedom are not idle, and neither are we", "Our government has taken unprecedented measures to defend the homeland- and we will continue to hunt the enemy before he can strike", are just a few of the examples that show that what President Bush meant was that the war on terror continued, and that America would continue being the leader on this hunt, without fail, and without rest.