I am so happy to see you (can you combine any words with an apostrophe?)
I'M = I am
My brothers teachers classes (the classes taught by ONE teacher of ONE of my brothers) / (where does the apostrophe go?)
My BROTHER'S TEACHER'S classes
My friends phones are all new (more than one friend) / (where does the apostrophe go?)
My FRIENDS' phones (the phones belong to my friends, more than one friend) / no apostrophe - 'phones' is a plural noun
Its sad that the cat broke its leg (where does the apostrophe go?)
IT'S (it is) sad / no apostrophe - second 'its' is a possessive pronoun
Its wagging its tail (where does the apostrophe go?)
IT'S (it is) wagging / no apostrophe - second 'its' is a possessive pronoun
Mrs. Hank marked _________ homework. (the student)
Mrs. Hank marked the student's homework.
My brothers teachers classes (the classes taught by ONE teacher of ALL of my brothers) / (where does the apostrophe go?)
My BROTHERS' TEACHER'S classes
The car belongs to Mr. Woo
Mr. Woo's car
My friends bag is new (one friend) / (where does the apostrophe go?)
FRIEND'S bag (the bag belongs to my friend, one friend)
Shes 16 years old (where does the apostrophe go?)
SHE'S = she is / no apostrophe - 'years' is a plural noun
Thats my parents car (both parents) / (where does the apostrophe go?)
THAT'S = that is / my PARENTS' car (the car belongs to my parents)
Thats Katys book (where does the apostrophe go?)
THAT'S = that is / KATY'S (the book belongs to Katy)
Those are childrens clothes (where does the apostrophe go?)
CHILDREN'S clothes (the clothes belong to the children) / no apostrophe - 'clothes' is a plural noun
My uncles wife is sick (where does the apostrophe go?)
UNCLE'S wife (wife of my uncle)