A question of possessive case

I don't know which one is better for exams.

1.) Everyone has one's problems.
2.) Everyone has his/her problems.
3.) Everyone has his problems.

thanks for your help.

Everyone has his or her problems.

This point has been discussed here before. While "Everyone has his or her problems" is correct, some people now say "Everyone has their problems". This is because some people find the use of "his or her" a bit clumsy. Of course, you could just say "Everyone has problems."

http://dinosaurhat.blogspot.com/2004/06/everyone-has-their-problems.html

i think it is correct everyone has his problem

but everyone has his own problem

[QUOTE]some people now say "Everyone has their problems". This is because some people find the use of "his or her" a bit clumsy[/QUOTE]

 Using "their" is incorrect because "everyone" is singular and "their" is plural. People make that mistake all the time in conversation but remember not to write it for an important exam/essay or something because it's incorrect grammar.

I understand why "everyone has their own problem" is incorrect. However, I am confused the usage of "his". I saw lots of American use "Everyone has his own problems". Is it correct when I write it down in exams?

Thanks for everyone's opinion.

Well, just saying "his" used to be acceptable but more commonly today people include women and say "his or her" because "everyone" isn't just male.