"Duo encourages us to study every day."
This sentence is very ambiguous.
I interpreted it as every day Duo is encouraging us to study, but the only "correct" translation seems to say that Duo is encouraging us to "study every day".
When reading sentences like this, visualize this
Subject + Verb + (Object + Time + Verb)
Yeah, that makes sense if you interpret the English sentence the same way Duolingo wants you to. But my first thought was Subject + Time + Verb + (Object + Verb), which I believe can translate to the same English sentence (though a slightly different meaning)