"This study is very important."
Translation:Cette étude est très importante.
I've noticed that sometimes Duo likes literal translations and sometimes it doesn't. This seems to happen regardless of whether it's referring to figures of speech, abstractions, etc. In English "study" is never used as a noun in the singular form, at least not that I'm aware of.
On the contrary, study is used frequently as a singular noun.
He keeps his books and important paperwork in the study.
This study established the link between ulcers and the bacteria Helicobacter pylori, H. pylori.