How to use Relative Pronouns?

The choice of relative pronoun often depends on whether the noun being referred to is a person, an animal, or a thing. In written English, who is used to refer to people, and which is used to refer to things. That is almost always used after everything, nothing, anything, something, only, all, and superlatives.

However, in many cases, and for TOEIC purposes, who and which are replaced by that.

For example:

When referring to people:

Who
It replaces subjects (people) in the relative clause.

Example: “The scientist who discovered the vaccine was awarded a Nobel Prize.”

In the example, who refers to the scientist and introduces the relative clause who discovered the vaccine.

When referring to animals and things:

Which
It can refer to the subject or object (things or animals) in the relative clause.

Example: “The experiment, which lasted five years, provided groundbreaking results.”

Which refers to the experiment and introduces the relative clause which lasted five years.

When referring to either people and things:

That
That is often used to define relative clauses (clauses that are essential to the meaning of the sentence). It can replace “who” or “which” in many cases, especially in informal speech or writing. Example:
“The medication that the doctor prescribed was effective.”
That refers to the medication and introduces the relative clause that the doctor prescribed.