"A girl is a child."
Translation:Девочка - это ребёнок.
No, это here can be roughly translated to "it is". Girl - it is a child. That's a very rough approximation but the thrust of it is that it is not denoting a specific child but the genre of girl in general belongs to the greater genre of children.
Russian only uses the present-tense 'to be' есть in specific constructions (like possession) and situations where unusual emphasis is placed on the existence or nature of something.
What are all the correct alternate answers for this, other than "Девочка - это ребёнок"?
Девочка, from what I've heard, is only used when talking about girls under sixteen. Девушка is used for adults/girls over sixteen, so it would be incorrect to say "Девушка - это ребёнок."
I don't think it's accepting the long dash (i.e. Девочка — ребёнок) in the translation, which is inconsistent with the rest of the course so far. Unless there's a difference between - and — that I don't know about?
I'm about 95% sure it's just a typesetting choice, and should accept the emdash if it isn't.
What's the difference between это, — and это —? It seems it has different meanings rather than the direct translation.
"Дети" means "children", "ребёнок" means "a child". It's a nonstandart plural form.