"Bäume braucht man doch!"
not only is 'one needs trees' not accepted, one of the correct answers is just wrong: "Man needs trees"
For a man, i.e. a human male to be a correct English translation, the German would be capitalised as it would be a noun, that is 'Mann' or 'Man'. However, 'man' lowercase in German is a pronoun which has two correct English translations: one or you (in the generic sense)
Lets do the following: I translate the German sentence with its full meaning as best as I can, and an English native speaker may give us some nice translation, and then we see how this would match with Duolingo. OK: "Bäume braucht man doch!" means, -this sentence makes only sense in German if someone has said the opposite before like: "(forget about all trees, we should cut them all down, for example.)"
Trees are needed, yes for sure!, One needs trees, for sure! Nevertheless, trees are needed. Everyone is welcome to make up a better English translation. :-)
There are many more ways to interpret this sentence since "doch" can be used in a variety of responses. It depends on the situation and the conversation leading up to this sentence. Some other possibilities: - People do too/indeed need trees. - People really do need trees. - So people need trees after all. - Actually, people do need trees.
"people" can also be switched out with "a person", "one" and in some cases even "you"
Well said Zerbo, if you start the sentence with: actually, however, after all, yet and use one, we, you or may be people in general and finish off with need trees, than you have a nice sentence which could be a reply to someone denying that trees are needed, or someone saying trees are obsolete or the like... 's that simple, the only adj. I personally wouldn't use is "but" in this case there are more suitable adverbs!! :-)