This one almost had me, every other course on here has me used to seeing "Duo" as a name.
Duolingo = Two languages.
Duo = the name of Duolingo's mascot. Hence the confusion.
I put "Two brothers sleeping" and it marked this as incorrect. Is "two brothers sleeping" truly incorrect?
"Two brothers sleeping" is just a noun phrase. The prompt is a complete sentence with a verb, so good translations are:
"Two brothers sleep."
"The two brothers sleep."
"Two brothers are sleeping."
"The two brothers are sleeping."
Awesome, thank you so much!