The correct answer is A) Athenian soldiers were able to hide in the valleys.
The geography of the Greek peninsula helped them defeat the Persians because Athenian soldiers were able to hide in the valleys.
On September 12, 490 BC, the strong Athenian army defeated the Persian troops in the Battle of Marathon. The troops of Persian King Darius 1, had conquered Thrace in the north of Greece. Most Greek city.states surrendered to King Darius army, except the Athenians and the Spartans. Although the Persians had a big army, it was not as well equipped like the Greeks.