The meeting was interesting. I went to it. (which)
The meeting to which I went was interesting.
I know a woman. Both of her children are girls.
I know a woman both of whose children are girls.
Olga wrote on a topic. She knew nothing about. (which)
Olga wrote on a topic about which she knew nothing.
The people were very hospitable. All of them invited us to their homes.
The people all of whom invited us to their homes were very hospitable.
The man was very kind. I talked to him yesterday.(whom)
The man to whom I talked yesterday was very kind.
Mrs. Lake is a teacher. I enjoy none of her lessons.
Mrs. Lake none of whose lessons I enjoy is a teacher.
I ran into a woman. I had gone to elementary school with her. (who)
I ran into a woman who I had gone to elementary school with.
This car has different features. Some of them are fascinating.
This car has features some of which are fascinating.
The candidate did not win the election. I voted for her. (whom)
The candidate for whom I voted did not win the election.
Their house was full of cats. Most of them had been found on the street.
Their house was full of cats, most of which had been found on the street.