the possessive form of everybody?

Hi, I would like to know the possessive form of the word everybody.
I've heard three different forms:

1. their:
''Jane Austen and other famous authors violate what everyone learned in their English class.''

2. your:
''Everybody move your body!''


3. his/her (its?):
''Everybody should respect his/her (its?) parents?

Thanks for your attention.

Everybody does take the singular, however the possessive form could be 'their' because, like 'some one', in modern English 'their' is now used instead of 'his' where the gender of the person/people isn't clear.

It can also be used as a second person imperative.

depends on who "everybody" refers to.

all the above are correct. for ''Everybody should respect his/her (its?) parents? " I would say "their" because everybody refers to all people

otherwise, "Each person should respect his/her parents"