"The cats are drinking tea."
Translation:Les chats boivent du thé.
"le" and "un" are not interchangeable. In both English and French languages, their use is defined by rules which are not always similar.
o DEFINITE ARTICLE "the" => le, la, les.
As their name explicits, they define nouns: the meal = le repas, is a specific meal, not any meal. Often, when you get longer sentences of a full text, you get hints by context. - ex: the woman eats THE meal that the cook prepared = la femme mange LE repas que le chef a préparé.
Note1: in English, when you claim a generality, like "men are stronger than women", the French use the definite article: "LES hommes sont plus forts que LES femmes".
o PARTITIVE ARTICLE => de la, du
When the object (what you drink or eat, for example) is not countable (countable:one strawberry, two strawberries), the French use DE+ definite article as a partitive expression. That is the case with water, milk, wine, bread, soup... of which you drink or eat only "some" of it, a part of it, a portion of it.
ex: when you get "cats are drinking tea", it means that they are drinking a certain quantity or tea: "some tea". So the translation will be "du thé", where "de" is a contraction of de-le.
cats are drinking soup = les chats boivent de la soupe (feminine noun)
The correct answer is "les petites chattes" instead of 'les petits chats' because of the pronunciation used by the talking lady. These phrases DO NOT sound the same; they sound different from each other. If you listen closely, she pronounces the last T at the end of 'petites' and at the end of 'chattes.'