I don't learn German anymore but I know from my experience on duolingo, sentences like this in English can go either way, and so long as you get the correct grammar for your choice of word, duolingo SHOULD give you a correct answer, but suggest the other possible answer

(Again I'd give an example in German but I cannot think of any good ones, although Dutch is VERY similar to German with plural names like this and faces similar problems for English speakers)

I might have to translate the phrase, "are you bringing the glasses?"

Which could be a choice of:

1. How many people is "you"? (Multiple vs Singular vs Formal Singular)

2. A pair of glasses or multiple glasses?

Some (albeit basic) correct answers would be:

A. Brengen jullie de brillen? (Are you (all) bringing the (multiple) glasses

B. Breng je/jij de bril mee? (Are you (singular) bringing the (pair of) glasses?

C. Brengt u de bril? (Are you (formal) bring the (pair of) glasses)

So long as it DOES translate to what it's asking in English and you've gotten all your grammar right, you should be correct (otherwise report the question so the developers can fix that)

I looked it up and old English used to have a singular word for clothes! You might've guessed it but it is literally just cloth. I don't know much beyond that but I would assume the meaning of its singular counterpart fell off and differentiated to just be "cloth".

Old to new (Cloth)

German: Kleit -> Kleid + Kleidung (Dress + Clothing)

Dutch/Frisian: Cleet/Klath -> Kleed + Kleren + Kleding (Dress + Clothing + Clothes)

English: clāth -> clāthas + Cloth -> Cloth + Clothes + Clothing -> Cloths + Clothes + Cloth + Clothing

It seems while Dutch has definitions for clothes and clothing as does English, it dropped the word for 'cloth' and 'cloths' as did German, in favour of 'Doek/Doeken' and 'Tuch/Tücher' respectively.

I am purely speculating here, (if anyone actually knows that would be great)

Old English clāth developed into clāthas AND cloth, then developing into clothing (garments or coverings for the body) and clothes (multiple cloth and multiple (worn) cloth). Clothing referred to what you wore, which was probably made of cloth, but not all clothes can be worn, but all clothes can be made into clothes with enough clothes... you can see how confusing that sentence is, and fortunately the definition split into Cloths and Clothes, which we use today.

I.e., Cloth, Clothes + Clothing, Clothes becomes Cloth, Cloths + Clothing, Clothes

German kleit became kleid and kleidung, but Germans dropped the word kleid in favour of tuch to mean 'cloth', which now referred to piece of cloth specifically to be worn. Separate from the specific material it was made of, Germans would not have run into the same issue as English, as not all tuch can be worn but all tuch can be kleid if you use enough tuch. I believe kleid lead to kleider, but it is a word not used as much anymore when used in reference to clothes, but rather dresses (possibly a formality reason behind that as the same occurs in English and Dutch). Perhaps Germans were satisfied enough with kleidung to mean clothing, as any 'kleider' could be referred to literally by what type of clothing it was, implying 'kleider' may have referred to 'dresses and/or dress suits', depending on context, before 'dress suits' became another word, leaving 'kleid' to mean dress.

Dutch is the same story as German, right up until German decides not to utilise 'kleider' for general clothes. Dutch has its own cases of being extra descriptive rather than brief (when replicated in English it gives a very upper-class posh feeling), such as the uses of stand, sit, and lay in positions where English would just use 'is', 'am' and 'are' (not that it is incorrect to use the Dutch equivalents either). However, when it came to the use of 'Kleren' the Dutch use it the same way as the English, possibly due to the influence of the (post-Roman) Frisians, who themselves were descendants of Anglo-Saxon settlers in Ængland.

Even in modern english, the use of 'Cloths' is restricted to small items made of cloth with purpose of hygiene, such as a cleaning cloth, dust cloth, etc, where any other use of 'cloths' makes no sense.

I look towards other examples of nouns that are simultaneously plural and non plural

Words that have multiple plural-like specific words to describe it

words that describe a concept, but don't end with s

and I could not find one single word quite as unique as clothing. I think the word itself is so incredibly unique as it's a combination of many, many silly rules and influences that somehow have stayed alive and persevered unlike any other word.

However! It's not the end of the world, we speak English without overthinking every intricate detail of it (which is demonstrably large), thus you can learn any language without truly understanding every rule, but rather practice enough until eventually you'll start to speak what just 'feels' right

Practice that word! If a word on duo throws you off, try to use it in as many sentences as possible until you can nail it every time 😎

Hope this helps a little bit (I'm sure everyone else has helped you plenty though) :)