I would be more interested in why it's "qui d'entre" and not just "qui entre" - is it because "qui" ends with a vowel?
"qui entre nous" would imply "who between us", literalrly between two people. whereas "qui d'entre nous" means "who among us" in a group of people.
Learner96's answer is correct. To give a tiny bit more explanation: The "d'" in question is the word "de" (of or from) with the e removed because the following word starts with a vowel. Literally, it could be translated "who from between us?" which is a perhaps odd way of asking "who in our midst?"
You can contrast this usage with the phrase "Entre nous," which is the french way of saying "Between you and me" (in confidence)
I got it wrong for writing this: Who is perfect among us? instead of this: Who amongst us is perfect? Isn't this too subtle a difference?
I think Duo doesn't like reversing the order of phrases in declarative statements even if it still makes sense. Duo accepts both among and amongst.
To allow moving phrases around would require much, much more complex programming for the machine.
Amongst is British usage or anachronistic American.
Among is contemporary American.
I got demoted for putting "who" rather than "whom" a while back.
Kind of confuses you as to which language we're here to learn...
Hey... I gotta admit, I've learned a bit of both while I've been doing this :)
There are very definite rules in English for who versus whom.
I hate getting getting mistakes for these kind of silly semantics.
I like to look at it this way... the more mistakes I report, the less that people after me will have to suffer the way I did :)