"There are various people."
Translation:Ci sono diverse persone.
"C'è diversa gente" means that there are several different people (various = different from one another); the meaning of "several" is actually stronger.
"C'è gente diversa" means that the people there are cumulatively different from other people.
The same with "persone", except that "persone diverse" doesn't specify if they're different from the people here or from one another.
"Gente" is a noun which, in Italian, is feminine but also singular although in English its translation "people" is plural, therefore we need the adjective also to be feminine and singular, which "diversa" is. "Persone", although also means "people", is a plural feminine noun therefore its adjective needs to agree with it, i.e to also be feminine and plural so we use the form "diverse" which is feminine and plural.
Because popolo isn't just a plural number of people. You're better off thinking of it as "nation" rather than people, in the American sense of the word, e.g. the Cherokee Nation: not a country, but a distinct independent culture.
As an example, in the Italian National Anthem there's the line "Noi fummo da secoli calpesti, derisi / perché non siam popolo, perché siam divisi": "We were for centuries trampled on, mocked / because we are not popolo, because we are divided". You can easily see why the plural "people" doesn't work: the singular "a people" does, as "nation" would.
Carolyn, it was marked wrong because "diversa gente" is singular, so you can't use "ci sono" with it. The next time you encounter that question, use "C'è diversa gente" and it should be correct. You need to keep an eye on what's plural vs singular, and that can be challenging with a word like "people" ('gente' (singular) vs. 'persone' (plural)).