Question

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

Explanation:

The Japanese achieved surprise at Pearl Harbor mainly because their aircraft carriers approached Hawaii without being detected. The Japanese carefully planned the operation, maintaining radio silence and using the vast expanse of the ocean to their advantage. They avoided major shipping lanes and used the element of surprise to launch a sudden attack. Land forces did not invade Hawaii in advance. Submarines were part of the overall operation but not the key to the surprise in terms of approaching the main target area in the way the aircraft carriers were. And the attack was on Pearl Harbor in Hawaii, not the US mainland.

Answer:

Japanese aircraft carriers had approached Hawaii unnoticed.