Question

how were the japanese able to surprise the us at pearl harbor?
o japanese land forces had invaded hawaii unnoticed.
o japanese submarines invaded pearl harbor unnoticed.
o japanese airplanes had flown to the us mainland unnoticed.
o japanese aircraft carriers had approached hawaii unnoticed.

Explanation:

The Japanese were able to surprise the US at Pearl Harbor mainly because their aircraft - carriers were able to approach Hawaii undetected. This allowed them to launch a sudden air - strike. Japanese land forces did not invade Hawaii before the attack, submarines were used in the attack but the key element for surprise was the aircraft - carriers, and the attack was on Pearl Harbor in Hawaii not the US mainland.

Answer:

Japanese aircraft carriers had approached Hawaii unnoticed.