"The animals drink water."
Translation:Gli animali bevono acqua.
il – masculine, singular, e.g. il libro (the book)
i – masculine, plural, e.g. i libri (the books)
la – feminine, singular, used before all consonants. E.g. la porta (the door)
le – feminine, plural, e.g. le porte (the doors)
lo – masculine, singular, with s+consonant or z. e.g. lo schermo (the screen)
gli - masculine, plural, with s+consonant or z. e.g. gli schermi (the screens)
gli - masculine, plural, begins with vowel e.g. gli anni (the years)
l’ – masculine or feminine, singular, begins with vowel e.g. l’anno (the year)
le – feminine, plural, begins with vowel. e.g. le università (the universities)
Notice how gli is used for masculine plural nouns beginning with a Z or S+consonant AND vowels. In this case animali is a masculine plural starting with the vowel A, therefore it is gli.
I found this link on another discussion post asking a very similar question: http://blogs.transparent.com/italian/using-the-definite-article/
Basically, the answer is because "gli animali" is a collective noun, and the subject of this sentence. It's ok to leave out the article in "Beve birra," because beer is not the subject of the sentence.
I was marked incorrect because I also chose the sentence "Animali bevono l'acqua." Why is there no definite article before water, yet it's in the answer? And if it is OK with that scenario, then why mark my second choice incorrect because I did not have a definite article. Duolingo seems to have a very unclear policy on when to use articles and when not to. :-(
In many cases, the use of articles is subjective. There are, however, certain instances when you should always use the definite article. This site was very helpful in explaining those rules: http://blogs.transparent.com/italian/using-the-definite-article/
In this sentence, "the animals" is a collective noun (one of the instances in which you should use the definite article) and "water" is more of a general concept rather than a concrete physical object in this sentence, and so doesn't require the definite article.