We repeat it almost every day, really. It is best to read the tips and notes first and ask for clarification. Most often "this"="tento, tenhle, tenhleten"+other genders, "that"="ten, tamten, tamhleten"+other genders.
Is "zvíře" pronounced accurately in duolingo? I keep hearing a hard "td" sound instead of what I thought "ř" should sound like, but it's entirely possible I've been misinformed, being completely new to this language. :)