I think the answer is unas
Because if you putter together is
Unas palabras because the word end in s and the other word end in s too so is unas
Nosotros somos de Guatemala.
Because ser is for more permanent things, like character traits or nationalities, while estar is more for temporary things like feelings or current location
How to remeber ser and estar easy
for how you feel or where you are, always use the verb estar
False. They are called proverbs or sayings.