Answer: The right answer is D) Characterized by treachery.
Explanation: The adjective "dastardly" specifically means cowardly, dishonest, treacherous and underhanded. Since the attack on the U.S naval base at Pearl Harbor by the Japanese on December 7, 1941 was a surprise and devastating assault, which caused the death of thousands of soldiers and civilians, FDR rightly used those forceful and unequivocal words to describe it in his address, which aimed at formally declaring war on Japan.
