You beat me to it. I would give you a lingot if you could do that on the phone version. :)
I think here we need to know whether we're using 'human' as a noun or an adjective. The noun 'human' is only going to be 'umano' or 'umani', whereas the adjective 'human' will be 'umano', 'umani', 'umana', 'umane'
For the record: 'We are humans' was also marked as correct, but the top answer is 'we are human'
Why does "umano" change to 'umani' for the plural but doesn't change to umana for the feminine?
Well, it does, for instance "the human race" is "la razza umana"; as a noun, it could be "un'umana" but that sounds like alien talk.
penelopelondon made a comment above about adjective and nouns. This lesson is about nouns so is not umane, umani the words used in this lesson true?
Weird and wrong. In my opinion, you can't have a plural verb with a single adjective.
See rogercchristi answer below: Subject + verb + adjective We + are + human
I would think that since "umani" is plural, the correct answer would be people or humans.
Sounds like something an alien would say...