Which sentence shows a restrictive relative clause with correct punctuation?

• A. The students who study regularly earn higher grades.
• B. The students, who study regularly, earn higher grades.
• C. The students who study regularly, earn higher grades.
• D. The students that study regularly earn higher grades.

Answer: (A)

Restrictive relative clauses identify exactly which noun we’re talking about, so they attach directly to the noun without extra punctuation. When the clause refers to people, who is the natural choice. In this sentence, the phrase who study regularly specifies which students are being talked about, and that information is essential to the meaning, so no comma is used. The result is clear and natural: The students who study regularly earn higher grades.

The other forms alter meaning or break rules about punctuation: adding commas around the clause makes it nonrestrictive and implies all students study regularly; placing a comma after the clause disrupts the restrictive flow; and using that instead of who is less preferred for people in formal writing. The best choice keeps the essential clause tight and uses who for people.