b) The Persians were not used to fighting at sea is your best answer choice.
It is not A), because the Persian ships outnumbered the Greeks by ~3 to 1.
It is not C), because with more ships, usually comes with more sailors & soldiers, leading to a larger proportion against the opponents. This means that Persia used more troops.
It is not D), because Sparta was known for their elite army (emphasize added), not their navy.
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