I am not saying that "they" cannot be used for things, but that it is by far not the first use of this pronoun and further that some people actually use "they" to mean "he or she". So it is already usable for indefinite gender and indefinite number. It is still the preference for many to use demonstrative pronouns instead for things. Common speech should be taken into account for this. https://www.merriam-webster.com/dictionary/they
It is not that "they" is wrong here, but that "these" or "those" could also be used here in common speech. https://www.merriam-webster.com/dictionary/this "this" can be "the person, thing or idea that is present or near in place, time, or thought or that has just been mentioned." and "these" is simply its plural. https://www.merriam-webster.com/dictionary/that "that" can be "the person, thing, or idea indicated, mentioned, or understood from the situation" and "those" is its plural.
Is this something a prescriptivist teacher taught you? It simply seems a vast impoverishment of a language to deprive it of a straightforward third person plural inanimate pronoun.
And dictionaries seem to provide no support for such a stricture (extracts from definitions of "they"):
- Oxford: Used to refer to two or more people or things previously mentioned or easily identified.
- Cambridge: used as the subject of a verb to refer to people, animals, or things already mentioned
- Merriam-Webster: used as third person pronoun serving as the plural of he, she, or it
- Collins: You use they to refer to a group of people, animals, or things.
- Macmillan: used for referring to a group of people or things that have already been mentioned or that are already known about
- dictionary.com: nominative plural of he, she, and it
- Webster's 1828: The men, the women, the animals, the things.
I don't really suppose this sentence sounds all that common in Dutch either (of course open to correction). I would imagine, that like I would suppose the case to be in English, a demonstrative pronoun would actually be more common in this sentence, but it's not a demonstrative pronoun that's there, so in the world of Duolingo translation, it seems unlikely anything other than the most straightforward, literal translation will be accepted. See, for example, course contributor Susande's response of a year ago in this thread.
"They" is used for things/objects all the time.
A: "Where are my shoes?" B: "I don't know. Aren't they in the closet?" A: "No, they aren't there."
A: "I wanted to go back and buy those pants I saw last time." B: "I walked by the other day. They aren't there anymore."
Perhaps the replacement of "they" by a demonstrative pronoun is due to a different dialect than Standard American English (which is what is predominantly used by Duolingo).
It is required to use "this" and "these" for an item or items that are near and "that" and "those" for those that are not close, but when location doesn't matter either can also be used instead of "it" or "they" in English. The fact is "they" is much more often replaced with demonstratives than "it" is, unless you actually want to indicate location.
Here's an explanation, from "Taal Unie", the official Dutch language center: http://taaladvies.net/taal/advies/vraag/380/het_zijn_incongruentie/
Such apparent mismatching of subject-verb "number" is termed an "incongruity". Makes Dutch fun to learn! (I wish I could have used that explanation for my mistakes in primary school! It would have been handy...)
But actually there is no mis-match. Linguistically, klompen is called a nominal predicate in such sentence structure. Thus, klompen takes the place of subject in the sentence, whereas in English, they is the subject. Therefore, the predicate subject requires a plural verb. The het? Well, that is the way the Dutch say it.
It English, "it" is always singular. The plural of "it" is they. So in English if you have two or more inanimate things (say, for example cars or boats or planes) the proper pronoun for them is "they". In Dutch, the proper pronoun for inanimate things is "het", whether you are referring to one thing (one car, boat, or plane) or more (at least two).
"Those" is used when singling something out Those are sandals (but these are flip-flops)
"They" is referring to something previously mentioned or when you are stating something (I have three apples) They are red or They are spools (and not pine cones)
Thus, both They are clogs (and not shoes) and Those are clogs (but these are shoes) are perfectly correct English, as long as they are used with their intended meanings.
I would just as soon say "These are clogs, not shoes." I would avoid using "they" when not talking about people, animals or plants. It would not matter if I said "these" or "those" in that case, because I am not focusing on location. "These are my reasons:....." or "Those are my reasons...." but I wouldn't say "They are my reasons..."