Rules for writers, Tenth edition - Diana Hacker, Nancy Sommers 2021

To refer to persons, use who, whom, or whose, not which or that
Make pronoun references clear
Grammar

In most contexts, use who, whom, or whose to refer to persons and which or that to refer to animals or things.

EXERCISE 23-1

Edit the following sentences to correct errors in pronoun reference. In some cases, you will need to decide on an antecedent that the pronoun might logically refer to. Possible revisions appear in the back of the book.

a. They say that engineering students should have hands-on experience with dismantling and reassembling machines.

b. She had decorated her bedroom wall with posters from chamber music festivals. This led her virtual classmates to believe that she was interested in classical music. Actually, she preferred rock.

c. In my high school, you didn’t need to get all A’s to be considered a success; you just needed to work to your ability.

d. Marianne told Jenny that she was worried about her mother’s illness.

e. Though Lewis cried for several minutes after scraping his knee, eventually it subsided.