The sentence that uses punctuation correctly is..
C) The discovery, which was the first of its kind in several years, caused an international stir.
Want to know why the answer is C? Look below! :D
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Let's look at the process of elimination -
° We know it's not A) because there are no commas to separate the subordinate and independent clauses, so it's just a run-on sentence.
° It would not be B) either because even though it has a comma, it doesn't have enough so this is almost a run-on sentence, too.
° Let's look at C) - Hmm, looks like it could be the answer, but let's keep looking at the other choices.
° The answer doesn't look like it would be D) because, just like B), it does not have enough commas to separate the subordinate and independent clauses, and, therefore, we are left with C)
→ C) is your correct answer. It separates the clauses perfectly and isn't a fragment or run-on sentence
↑ ↑ ↑ Hope this helps! :D
