What allowed the small Greek army to hold off the larger Persian army for three days?

The Greeks held the narrow pass at Thermopylae, where the Persian army could not bring its much larger numbers to bear all at once. The mountain pass therefore helped the smaller Greek force hold off the Persians for three days. Choice A, “The Greeks fought the Persians in a small mountain pass,” gives the reason.

AI-written and checked against the verified answer.