ACT English Relative Clauses: Use Who/Whom and That/Which Correctly

Who is a subject; whom is an object. Test: Replace with he/him. If he works, use who. If him works, use whom. Example: "The student who solved the problem" (he solved it; who is correct). "The student whom I tutored" (I tutored him; whom is correct). That introduces essential clauses (necessary information). Which introduces non-essential clauses (extra information). Example: "The book that won the award" (essential; which book? The one that won). "The book, which won an award, became famous" (non-essential; extra info). These distinctions are mechanical: test with he/him for who/whom; use commas and meaning for that/which.

Key rule: If a clause needs commas around it, use which. If it doesn't need commas, use that. If you can remove the clause without changing the sentence's core meaning, it's non-essential; use which.

Mistake 1: Using who when whom is correct (or vice versa). Always test with he/him first. Mistake 2: Using that for non-essential clauses. "The car, that was red, was fast" is wrong. Use which for the non-essential clause: "The car, which was red, was fast." Mistake 3: Using which for essential clauses. "The car which I bought is broken" should be "The car that I bought is broken" if the clause is essential (specifying which car). Remember: which usually has commas; that usually doesn't.

During practice, test who/whom with he/him, and check for commas around clauses to determine that/which.

Sentence 1: "The teacher who I respect." Error: Test with him? "The teacher him I respect" doesn't work. Use whom: "The teacher whom I respect." Sentence 2: "The athlete that won the medal was humble." Correct (that for essential clause, no commas). Sentence 3: "The book, that was old, fell apart." Error: Non-essential clause with that. Fix: "The book, which was old, fell apart." Sentence 4: "The student whom solved the problem is brilliant." Error: Test with he? "The student he solved it" works, so use who: "The student who solved the problem is brilliant." Sentence 5: "The rule which applies here is clear." Depends on whether the clause is essential. If essential (specifying which rule): "The rule that applies here is clear." If non-essential (just extra info): "The rule, which applies here, is clear."

Find 10 relative clause questions from a practice test. For each, test who/whom with he/him and check commas. By the tenth question, relative clause correctness will be automatic.

Relative clause questions appear regularly on ACT English. Because the rules are learnable (test with he/him; check commas), this is a high-return skill. Mastering who/whom and that/which picks up 1 point on the English section because the distinctions are consistent and mechanical.

Drill these distinctions daily this week. On every practice test, mark every relative clause and verify who/whom and that/which are used correctly. By test day, you'll spot relative clause errors automatically.