To show possession for a singular noun (like "cat"), you add an apostrophe followed by this letter.
S
The skateboard belonging to Ehud
Ehud's skateboard
(It’s / Its) a very sunny day in the valley.
It's
Who are these beloved literary characters?

Frog and Toad
The three singers microphones were all turned off.
singers'
If a plural word already ends in "s" (like "drivers"), you place the apostrophe in this location.
After the s
The office shared by Judi and Maria
Judi and Maria's office
The dog wagged (it’s / its) tail happily.
its
A writer might use a dash instead of this punctuation mark if they want to indicate a "stronger" or more dramatic break.
Comma
I went to my doctors office for a checkup.
doctor's
These shortened words, such as "don’t" or "shouldn’t," always require an apostrophe to represent missing letters.
The separate, individual lockers of Roland and Isabel
Roland's and Isabel's lockers
I borrowed (Mark / Mark's) and Remi's shared textbook.
Mark
When a dash follows a list prior to a summary or explanation, it acts like this other punctuation mark in reverse.
Colon
Most of the students' preferred to study in the library.
students
True or False: Possessive pronouns like hers, ours, and yours require an apostrophe.
False
The meeting of the supervisors
The supervisors' meeting
Both (players’ / player’s) jerseys were covered in mud after the game.
players'
Who is this?

Captain Barnacles
We are celebrating Mothers Day at a fancy restaurant.
Mother's Day
When two people share ownership of one single item, the apostrophe goes on which person’s name?
The last owner mentioned
The toys belonging to the children
The children's toys
I think (your / you're) going to love the surprise!
you're
What is the name of this moon?

Io
That backpack is their's, not mine.
theirs