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Standard English ConventionsMediumEssential 'who' clause takes no commas

Standard English Conventions practice question

The early check-in rule applies only to international flights. Passengers ____ must check in at least two hours before departure.

Which choice completes the text so that it conforms to the conventions of Standard English?

  1. A. who are flying internationallyCorrect
  2. B. , who are flying internationally,
  3. C. who are flying internationally,
  4. D. , who are flying internationally

Answer: A. who are flying internationally

The first sentence limits the rule to international flights, so 'who are flying internationally' is essential — it identifies WHICH passengers. Essential clauses take no commas.

Why the other answers are wrong

B. , who are flying internationally,
Commas would make the clause an aside, implying ALL passengers are flying internationally.
C. who are flying internationally,
A lone comma after the clause separates the subject from its verb 'must check in'.
D. , who are flying internationally
A lone comma before the clause has no partner and wrongly signals the clause could be dropped.

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