Children -- hate chocolate are uncommon.
who
They live in a house. The backyard of the house is full of flowers.
They live in a house whose backyard is full of flowers.
An elephant is an animal. This animal lives in hot countries.
An elephant is an animal which lives in hot countries.
My friend Peter went to High School with me. He´s written a novel.
My friend Peter, who went to High School with me, has written a novel.
The castle -- we visited last year was very nice.
which
The sports center has recently opened a new tennis court. I go swimming there.
The sports center, where I go swimming, has recently opened a new tennis court.
This bike cost a fortune, it was made in Germany.
This bike, which was made in Germany, cost a fortune.
Did you like the song? I wrote it.
Did you like the song that/which I wrote?
I was born in this city, I also want to study and live here.
I want to study and live in the city where I was born.
The girl is very sad, her doll was lost.
The girl whose doll was lost is very sad.
I facetime my best friend twice a week. She lives in Ontario.
I facetime my friend, who lives in Ontario, twice a week.
