Which of the following is a correct sentence (that is, not a comma splice or run-on sentence)?
Harold realized that the train was late he was standing on the subway platform.
Harold realized that the train was late, he was standing on the subway platform.
Harold realized that the train was late Harold was standing on the subway platform.
Harold realized that the train was late while he was standing on the subway platform.



Answer :

The correct sentence among the options provided is:

"Harold realized that the train was late while he was standing on the subway platform."

Here's why this sentence is correct:
1. It combines two related ideas using a subordinating conjunction "while." This conjunction helps to connect the two clauses in a way that shows the relationship between Harold realizing the train was late and him standing on the subway platform at the same time.
2. The use of "while" in this sentence makes it a complex sentence where the first clause ("Harold realized that the train was late") is the independent clause, and the second clause ("while he was standing on the subway platform") is the dependent clause that provides additional information about the timing of the realization.

By using "while" to connect the two clauses, the sentence avoids being a comma splice (where two independent clauses are incorrectly joined by a comma) or a run-on sentence (where two independent clauses are incorrectly joined without appropriate punctuation).