Time to call out another extremely common mistake:
ITS vs. IT'S
It boils down to a simple rule. Which is: POSSESSIVE PRONOUNS NEVER USE APOSTROPHES.
Admittedly, this rule means nothing to you if you don't know what a possessive pronoun is. So let's spend a minute on this:
POSSESSIVE PRONOUNS are pronouns that show ownership. As in, something BELONGS to someone or something.
In a sentence, a possessive pronoun acts as an ADJECTIVE, because it will always modify a noun:
So, here they are, in all their glory:
HIS, HERS, ITS, THEIR, THEIRS
There it is, right in the middle of the last list: ITS. Meaning, "belonging to it." NO APOSTROPHE.
NONE of the possessive pronouns have apostrophes. NOT EVER.
So, what is IT'S all about?
IT'S is a CONTRACTION that stands for IT IS. The apostrophe in a contraction always takes the place of missing letters. In this instance, it takes the place of the letter i.
IT'S raining today. (Meaning: IT IS raining today.)
IT'S hard writing novels. (Meaning: IT IS hard writing novels.)
If so, you'll see why it's ridiculous to say:
The baby fell asleep in it's crib.
The meaning of which is: The baby fell asleep in IT IS crib.
And there's your litmus test. Since IT'S always means IT IS, check by substituting IT IS for the IT'S in your sentence. If it doesn't make sense, YOU'RE WRONG.
Because...POSSESSIVE PRONOUNS NEVER GET APOSTROPHES.
I understand why it's confusing. "Normal" nouns get an apostrophe-S to connote ownership:
Mad's black belt
But if you can remember that POSSESSIVE PRONOUNS NEVER GET APOSTROPHES, you will never use IT'S when you're supposed to use ITS.