The smartphone is an invention who /which/where has made people's lives easier than before.
which
My English teacher is a person which / who / where really encourages me to work hard.
who
The room which / where I study is always cool in the summer.
where
A cassette recorder is something which / where / who you don’t see very often these days.
which
The children which / that live in my apartment block are very polite.
that
The woman who / which found my wallet gave it to the police.
who
We visited one town that / where most of the buildings were new.
where
The map that / where we had was very easy to use.
that
I think the food which / who / where we ate last night was Mexican.
which
Nelson Mandela was one of the greatest men that / which ever lived.
that
