Here are the corrections for the possessive pronouns in the practice exercises:
Koji is wearing shoes.
His shoes are black.
His
Ellada and Jena are wearing jeans.
Their jeans are blue.
Their
She is wearing boots.
Her boots are old.
Her
Dirk is wearing a hat.
His hat is blue.
His
Ben has a coat.
His coat is brown.
His
Steve and Tia have a car.
Their car is old.
Their
Susan has a book.
Her book is very big.
Her