Translation:In the series, there is a black cat, who can talk.
"Who" is reserved for things that take human pronouns. Pets and animals regularly take human pronouns and so can be referred to as who (e.g. Who's a good boy? vs Which is a good boy?).
The converse is not true for "that". Things that take human pronouns may also be referred to with "that".
This is a rather confusing point about English grammar. When choosing a conjunction, you have to think about whether the subject takes human pronouns and whether the clause is restrictive (essential to the meaning) or nonrestrictive (providing additional info; separated with comma). In my own dialect, the conjunctions are:
- That: Always restrictive clause; Subject may be it, he/her, or they (some other dialects avoid using this for he/her/they)
- Which: Always nonrestrictive; Subject must be it or (non-human) they
- Who: May be restrictive or nonrestrictive; Subject must be he/her or they (some other dialects avoid using this for restrictive clauses)
Those that prefer "that" over ", who" feel that cat's ability to speak is essential to the meaning of the sentence. I agree with this judgement, however my dialect would only require the comma be removed and not necessarily that "who" be changed to "that".
People don't really bother much nowadays, but the correct answer depend on the meaning that you wish to convey:
1. If the important feature is the talking rather than, say, riding a motor bike, you are defining the cat and should say '..black cat that can talk...' .
2. a) If the talking is not the defining feature of the cat, you would say '..black cat, which (by the way) can talk, ...' In this case, there should be commas after cat and talk (equivalent to brackets).
b) You could, however, use 'who' instead of 'which' if you want to stress the cat's human-like quality of speaking a human language.
Translations from one language to another (especially unrelated languages such as English and Finnish) in a course like this are often clunky. The original, given translation is equally clunky. I would much rather have a clunky but accurate and literal translation than a smooth but inaccurate one.
I understand the feelings of frustration behind these comments. I've been there. When I was learning Japanese I would complain. But once I gained fluency I realized that the Japanese grammar was so different from the English that a good or bad translation into English was beside the point. And the grammatical correctness of the translated English was completely irrelevant for purposes of learning. Learning the patterns in The target language is what's important. I have been translating and transcreating Japanese into English for decades. I am paid up to USD 10,000 (not a typo) per word, if that opens your mind to what I'm saying. To translate you need to understand the context of the source sentence. Grammar of the source text is often distracting and the source text itself is frequently poorly written. So I need to know how Japanese works. That's what grammar is. But English doesn't work at all like Japanese. Once I understand what the source writer is trying to say, I simply write how you would express in English what the author meant to express in Japanese. Rarely do the grammatical constructions have a one to one relationship. "An accurate translation is a bad translation" in this kind of work.
I find myself in agreement with this. Granted, I'm not truly fluent in any language but English, but I know that it is far more helpful for me when attempting to learn a language to have a "poor" English translation (meaning one that may take many extensive liberties with proper English syntax) that is closer to the target language (in this case, Finnish) and thus helps me better understand how the target language works.
Having proper English is nowhere near as important as getting a feeling for how words are put together in the target language. I'd far rather have an accurate but clunky English translation that follows the target language perhaps a bit too literally, than a proper English one that sacrifices any feel for how the target language works.
I've felt very similarly when learning languages; you don't want a course formally teaching improper grammar, but looking at word-for-word glosses can give you a feel for thee target language while understanding the meaning of the words in your native language, as can looking at the L1 interference target-language speakers struggle with in your learning-langauge.
"No speak English" is exactly how no hablo inglés would translate word-for-word. Understanding why Spanish speakers might say it that way in English gives you a feel for the rhythm of Spanish: you can pick up that Spanish drops pronouns (especially "I") and negates verbs by placing "no" directly in front of the verb.
Or take "long time no see", originally from the pidgin English used by Chinese laborers as a calque of 好久不见. The English calque hints at the lack of grammatical inflection present in Chinese (i.e., word stems are not changed to indicate details such as number or verb tense).