Recall from last week that who is used when you need a subject, and whom when you need an objective pronoun. But in addition to who, there are other subjective pronouns. Select who when the individual or the individuality of the group is meant, and that when a class, species, or type is meant.
- She is the only one of my teammates who can beat Serena Williams.
- He is the kind of player that should win the Grand Slam three years in a row.
Which and that are used when referring to places, objects, and animals. Which is always used to introduce nonessential clauses, and that is ordinarily used to introduce essential clauses.
- Timmy's story on the national championships, which I sent you last week, should be of some help. (Which introduces a nonessential clause.)
- The story that I sent you last week should be of some help. (That introduces an essential clause.)
Which, that, and who may be used to refer to organizations. When you are referring to the organization as a single entity (in other words, as it), then use which or that. However, when you are thinking of the organization in terms of the individuals who make up the organization (in other words, when you think of the organization as they), you may use who or that.