I want to know the answer to the following question:
What were the most vital American ships at the time of the attack?
All the background I'm provided with is that "American losses were less serious than initially thought: The American aircraft carriers, which would prove to be more important than battleships, were at sea, and vital naval infrastructure (fuel oil tanks, shipyard facilities, and a power station), submarine base, and signals intelligence units were unscathed.". Is that enough to answer the question?