This is just verbatim from the lesson, but I don't think you can access the lesson from the phone app.
Ke vs. Ka
"Ka", "Ke" and "Nā" are determiners that can sometimes be translated as "the". Use ke when the noun that follows begins with the letters K, E, A, or O. Use ka with almost all others! This is commonly referred to as the KEAO rule. Warning: there will be exceptions (don't worry, we'll let you know which ones they are!).
Nā is only used to say "the" when the noun is plural. Certain words like "wahine" are pronounced with a longer "ā" when plural and hence spelled with a kahakō (macron), "wāhine".