I was stumped by this one too. Of course, I put several, but got it wrong. So I looked up several in the dictionary and it means "separate, distinct; different, respective; or more than 2 but not many; few; a small number of" I know most of us use several to mean lots of something, but evidently, we are using the word wrong. Multiple obviously means quite a few, the dictionary says here "having many parts, elements, etc; 2 shared by or involving many; a number which is a product of some specified number and another number" However, just under that we find "Multiple choice which means "listing "several" answers from which the correct one is to be chosen". So although multiple means many and several means a few, the dictionary explains that we use the word multiple to give just a few answers to choose from, usually 3. Go figure. Our language is a mess! But looks like DuoLingo is right in saying multiple here, whether or not the sentence makes sense to us. Diverse on the other hand is a stretch, it has more the meaning of varied not numerous.
My understanding is - and let native speakers of Spanish correct me if I am wrong - that 'multiples' does not necessarily mean the same as 'muchos', it just means 'more than two' and is, therefore, synonymous with 'several'. Thus, 'My sister has several coats' should be accepted as a correct translation. In fact, speaking of clothing, no one says 'multiple coats' in English.
When I looked up múltiples online, I got very few results, but those I did get seemed to indicate it meant many. After reading your comment I looked again and found (at the FreeDictionary.com site) that you are correct, it can mean more than one. I am not a native spanish speaker, so I cannot speak for them, but I think you are on the right track.
There is absolutely nothing wrong with 'multiple coats' in English and I'm sure it's something that I have said plenty of times.
There is absolutely nothing wrong with using the words 'affirmative' and 'negative' for 'yes' and 'no', respectively, - they always do it in the military force - although the words sound funny to a civilian's ear. Likewise, 'multiple coats' sounds like playing with words rather than the more obvious choice 'several coats'
I see it's been a year, so you may have already found the answer, but for the benefit of others reading this thread--
I'm guessing you mean "before", not "after". While adjectives usually come after nouns in Spanish ("abrigo azul", "abrigo grande", "abrigo viejo", etc), from what I can tell (I'm not a native speaker), adjectives of quantity usually come before the noun, just like numbers. So "siete abrigos", "unos pocos abrigos", "varios abrigos", "muchos abrigos", "múltiples abrigos", etc.
Tener means “to have”, but as with all Spanish verbs, that changes with the person. So to say “you have” in Spanish, it would be “Usted tiene”. ¿Cuántos años tiene? literally means “How many years do you have?” ¡Aquí tiene! literally translates to “Here you have” but it means in English “Here you go!” In English if we use “you” with “have”, it sounds fine, but if we say he, she or it we change the verb to has. In Spanish, the verb remains “tiene” but translates to “has” in English. So, "Mi hermana tiene múltiples abrigos." translates to "My sister has....(I refuse to use multiple here) many coats." I hope this hasn’t confused more than helped you.
I agree that 'diverse' and 'multiple' are completely out of place here and 'several' or 'many' would any day serve the purpose better. Sometimes DL tries to experiment with words, thus inadvertently assigning new meanings to common, mundane, everyday expressions, in addition to beguiling the poor learners no end.
Clearly, "multiple" is not a usual English translation. After some research, Google (of all places!) says: "múltiple -- Que tiene más de un elemento, está formado por diversas partes o aspectos, o se manifiesta de muchas maneras" -- information that the "many" skirts are substantially different. I like subtle way the Duo reminds us of these subtle differences in languages :)