Answer:
B). ASIA.
Step-by-step explanation:
As per the question, the US military officials expected that the Japanese would attack southeast Asia which they had planned as a preventive action but their sudden and surprising attack on Pearl Harbor left them speechless. Japanese military's unanticipated attack on Pearl Harbor dated 7 December, 1941 led the United States to conventionally enter the World War II. The key cause of this attack was US army's interruptions and attempt to freeze the assets and exports of the Japan and thus, this took United States to officially land its foot in second World War. Therefore, option B is the correct answer.