Contractions

Within the text of a novel, it’s best to use contractions. Here are a few:

Its or It’s
The contraction of it is = it’s
The possessive term of it = its
Examples:
It’s my Birthday.
My dog wags its tail.
I leave my house by its front door.

There is no such term its’

Who’s or Whose
The contraction of Who is = Who’s
The possessive word of who = whose
Examples:
Who’s paying the bill?
Whose house is this?

They’re or Their
The contraction of they are = they’re
The possessive term of they = their
Examples:
Bill said they’re his clothes.
The problem is their fault.