Could someone please explain why "Who teaches them" is wrong? Thanks!
It is! And I see that you have suggested it a minute ago (i am guessing it was you based on time) and your suggestion turned green, telling us that the sentence is already in the system. The last time anybody edited this sentence was a year ago. There goes Duolingo for you.... Not much we can do when it refuses to work as it should :(
Yep, that was me... I figured I might as well "report" it, too, and see what happens. Thanks for the fix!
UPDATE ---- Still doesn't like "Who teaches them," so I guess this is just some weird system thing that's not going to go away. Oh, well.