The correct answer is D) to put forth a united opposition to the attacks.
The main purpose of mentioning the will of the Congress and of the people here was to put forth a united opposition to the attacks.
After the terrible attack of the Japanese army over Pearl Harbor island, in Hawaii, President Roosevelt delivered the "Infamy Speech" in Congress on December 8, 1941.
During the Speech, Roosevelt referred to the will of Congress like this "I believe I will interpret the will of Congress and of the people when I assert that we will not only defend ourselves to the uttermost but will make very certain that this form of treachery shall never ender us again.
So we can conclude that the main purpose of mentioning the will of the Congress and of the people here was to put forth a united opposition to the attacks.
