USING THAT, WHICH, AND WHO
Which and that refer to things, animals, or anonymous collective groups of people.
That is used to introduce the necessary, or restrictive, elements of a sentence.
The filing cabinet that stood in the corner was empty.
The group that vacated the hotel left quite a mess.
Which, though commonly used interchangeably with that, is most often used
to introduce .the nonessential, or nonrestrictive, elements of a sentence.
Our house, which looks quite similar to every other house on the block,
is on the corner of Wilhelm and Third.
The tree, which had been pruned only recently, was felled by the sotrm.
Who is used in association with people, or animals with names and special talents.
Our cat, Bobo, is the one who knocked over the lamp.
The man who stopped to help when our car broke down neglected
to tell us his name.