Question: WHen did they find the polish kingdom?

Is "The szlachta traced their descent from Lech/Lekh, who probably founded the Polish kingdom in about the fifth century.:482 Lechia was the name of Poland in antiquity, and the szlachta's own name for themselves was Lechici/Lekhi.:482" the correct answer?
Available choices:
1). yes.
2). no.
1).