"Which/who/that are/is", how do you know which one is correct?

[Deathknightish]

This is one aspect I never learn to understand in English.

Let me give an example:
"There are groups, <blank> are trying to subjugate the entire world!"

HOW do you know if "which", "who" or "that" fit into the <blank>? What are some rules and guidelines to look for to make it easier?

[Elegiac]

They're fairly interchangeable - as long as you can make yourself understood sufficiently it really doesn't make that much of a difference.

[shadowmouse]

Others have already given good answers, but something to keep in mind is what you are emphasizing. Remember, there are also some differences in perception (is a group people or a thing) between British and American speakers. As an American, I'm going to tend to go with who if I'm focusing on the people in the group and otherwise that.

[muto]

That are and no comma needed.

[Cinnamilk]

https://www.grammarbook.com/grammar/whoVwhVt.asp

A little more detail. Check out what they call rule 2, dealing with essential and nonessential clauses.

[shadowmouse]

For more fun with English, I give you conjugation! <bungee is frustrated with headlines that show American English turning to -ed for everything>

https://grammarist.com/usage/shat/
https://conjugator.reverso.net/conju...to%20shit.html

[Wyrt]

"There are groups that are trying to subjugate the entire world!"

No comma.

Who is for people, and while groups are made up of people, they are not people themselves.

Which would be used if the sentence was more like: "There are groups, which are growing in number, that are trying to subjugate the entire world!"

[Shadowferal]

I always equated the "s" in the word "is" as "singular."