that has.

listen to the pronunciation of that has.
English - English
that's

I've managed to find the solution to the problem that's been bugging me all day.

This is the best thing that's ever happened to me. - This is the best thing that has ever happened to me.

You're the best thing that's ever happened to me. - You are the best thing that has ever happened to me!

That is.
that's

That's the book I've been looking for.

That's my dictionary. - That is my dictionary.

That's a useful piece of information. - That is a useful piece of information.

someone has.
someone's