Hi Nattarika, Yes you can also use 'people' and it will make sense. However, the meaning of the sentence will change. 1) people - Means that the nuclear apocalypse may have killed a few people, a lot of people or everyone. 2) everyone - More specific than people. Means that all the people died. Hope this helps!

well, if you want to replace it, then it'll be "all people", as everyone literally means every last person. Everyone will sound more natural in speech than all people though.

These words typically carry different connotations. "Everyone" = all of the people, e.g. on Earth, in the room, in the city, etc. "People" = many human beings "It's been 97 years since a nuclear apocalypse killed everyone on Earth..." -> This means that no humans survived, and there were no humans left after the apocalypse. "It's been 97 years since a nuclear apocalypse killed people on Earth..." -> This means that some people died, but not everyone. Some people survived after the apocalypse.