During Major Historical Events Such as the Attacks on Pearl

During major historical events such as the attacks on Pearl Harbor in 1941 and on the World Trade Center and Pentagon in 2001, why does the role and position of president become so important?

A) The constitution requires that Americans follow the president's advice.
B) The president becomes a strong voice to command the nation's attention, calm fears, provide direction, and employ resources.
C) Congress is often unwilling to lead during emergencies so the president's role and authority increases.
D) The states have sole power to respond to threats against them by foreign powers but they rely on the president for guidance.
E) Congress is incapable of taking any type of action against foreign enemies so this responsibility is left to the president.