So the word for 'person', osoba is also feminine in Slavic languages, regardless of gender, without it being a loan from Latin. Awesome.
What's the difference between osoby and lidé?
Osoby (fem) is closer to "persons, individuals"
Lidé (masc anim) is closer to "people, humans, men..." The singular of lidé is člověk.
"Those are young people" was marked as wrong
That would be "To jsou mladé osoby";;