You probably learned the english "the" with a "d/z"-sound, but "th" in the, they, ... is actually the sound /ð/. It's called the "voiced dental fricative", which means you have to pronounce it like a "d" or "z" but with your tongue in between your frontal upper&lower teeth. [/ð/ = greek δ = this] [/θ/ = greek θ = thin] ( /θ/ is like a dental s).
Providing the correct context--for instance, if one were to ask, "What is she doing?" (I believe this translates to τι κάνει;, but, please, correct me if I'm wrong--I think τι κάνει; means more like, 'How is she?' or 'How is she doing?'), could another respond with simply the verb and the correct ending (διαβάζει) as a response?
I'm not asking for a Duolingo concept--just wondering if this is what would be done in Greece itself.
Please read the Diphthongs section in the Tips and notes in the ABC skill: https://www.duolingo.com/skill/el/ABC/tips-and-notes. :)
Think of the Greek verbs in a pyramid formation. The four blocks at the base are the perfects the 3 above are the simples and the two above them are the imperfects and the one at the top is the continuous. You only need 4 tenses Imperfect past I was reading διάβαζα, simple past I read διάβασα, simple present I read/am reading διαβάζω and simple future I will read θα διαβάσω. By adding θα you can obtain all the other tenses Imperfect future I would read θα διάβαζα, Continuous future I will be reading θα διαβαζαand apart from these the 4 perfects which you add έχω or είχα along with θα. είχα διαβάσει I had it read, έχω διαβάσει I have it read, θα έχω διαβάσει I will have it read, θα είχα διαβάσει I would have it read. In there case you conjugate the έχω and the είχα to denote the person.