We use apostrophe +s (‘s) to talk about things associated with one person:

My friend’s name is Natalia.

These are my husband’s things.

We uses s + apostrophe (s’) to talk about things associated with more than one person:

Here is my sisters’friend.

The students’records are in the cupboard.

Note that we use an apostrophe + s (‘s) with irregular plural nouns:

The children’s party is at the club.

We also use apostrophe +s (‘s) on it’s own:

My birthday is the same day as my mother’s.

We use of to talk about things associated with places and objects:

Madrid is the capital of Spain. (not Spain’s capital)

The answers are at the back of the book.