Tatiana, a palavra "this" quer dizer "Este, esta, isto", Esse pronome é usado para demonstrar ou identificar algo que está próximo de nós, por exemplo: “This book is yours.” (Este livro é seu). No caso dessa questão do Duo, está sendo utilizado o "That", pois "desse (a), esse (a) e aquele (a)" está se referindo a algo que não está próximo, ou seja, não é possível tocá-lo sem se locomover. Espero ter ajudado. > 05.06.2016
I disagree. Using your example, there is an implied verb. In this case, it would be "I like studying genocide". Those concepts are not mutually exclusive, and I would think a native Portuguese speaker would recognize and accept this. In fact, I asked a native Brazilian Portuguese professor at my alma mater(who is also coincidentally my significant other :) ) and she replied that it is perfectly fine Portuguese.
This is really badly explained here! If i understand it right, deste mean this (close to me), desse still this, but close to you (or the other), and daquele that (far from both you and me). At least that is what is explained on the duolingo forum. So why does it not accept she likes THIS newspaper, as it is close to her (and not me)? If it is impersonal and far from all why is it not use daquelo? Some explanations would help to overcime this concept unknown in English!