Final answer:
The letter from George Bush was addressed to Congress, where he declared a war on terrorism and presented the Bush Doctrine following the 9/11 attacks.
Step-by-step explanation:
The letter from George Bush that is mentioned likely refers to an address made by former U.S. President George W. Bush. This particular address was not sent to an individual recipient such as his wife, the vice president, or the military. Based on the provided context, which speaks about a national address following the events of 9/11 and the subsequent war on terrorism, the correct recipient would be Congress. On September 20, 2001, in an address to a joint session of Congress, President Bush declared a war on terrorism, demanded that the Taliban turn over Osama bin Laden, and presented his stance that would become known as the Bush Doctrine. Hence, the correct answer to the student's question is option c. Congress.