In the lesson that introduces gatte, there is no mention that such means female cats. In the lesson for gatti, there is no mention that it could be all males, unknown genders, or cats of mixed gender. That makes the lesson confusing. Plus they define it in gutti as cats or cat but count you wrong if one uses cat. This info should be added to the site.
Good thing one can check out comments, or one would be clueless.
I'm not certain on this, but l'acqua sounds more like a bit of water the listener acknowledges, while acqua is the idea of water. In this case, it would mean the cats do drink water, but aren't neccessarily in the proccess of drinking at the concern of listener. This is merely how I understand it, correct me if I'm wrong.
I might be wrong here but why isn't the proper translation for il gatto "tomcat"? In German it would be Kater (male) as opposed to Katze (female). Most (if not all) animals actually have a different word for male and female. Just mentioning stallion and mare (horse), dog and bitch... So it would be nice if duolingo accepted the word tomcat.