ACT Standard English Practice Test 2026 – Complete Exam Prep

A relative pronoun starts a clause that describes or identifies a noun. In The city that never sleeps, the part that never sleeps is a relative clause modifying city. The word that begins this clause and serves as the subject of the verb sleeps, referring back to city, is the relative pronoun. Who and whom are for people, so they don’t fit. Which can refer to things, but in a sentence like this that introduces essential information about a specific city, the conventional choice is that (without commas). So the correct word is that.