"How are they?"
Maybe the notes should include how this works? Hover tips didn't help at all hardly?
You can see notes for this lesson, when you will use duolingo on computer. Unfortunately application does not include grammar notes.
It's correct, but I think Duolingo is limited to giving us 1 answer, because it's the computer correcting us and not a real fluent Chinese teacher, so those 2 options may not be correct until true artificial intelligience is created.
Your examples are fine sentences, but they are too narrow in my opinion. Your sentences are asking "Are they good?" (which is a specific yes/no question) instead of the open-ended "How are they?"
One is he, and add "men" to make it plural male. The other is she, and add "men" to make it female plural.
If you said "她们很怎么样？" It wouldn't make a lot of sense. Translation: Very how are they? It sounds like Doge.
BTW if you don't know what Doge is, search "Doge meme".
It depends on the context; if 'they' is referring to a group of women or a group (of men). If the group consists of only women, then it is 她们。
I don't understand sentence structure. Is this question literally translated, "They are how?"