Final answer:
The most effective sentence combination is: My great-grandfather, who is sitting over there, received a Bronze Star in World War II.
Step-by-step explanation:
The most effective sentence combination that uses correct punctuation is: My great-grandfather, who is sitting over there, received a Bronze Star in World War II. This sentence combines the two independent clauses with a relative pronoun and uses the appropriate comma placement. The relative pronoun "who" introduces additional information about the subject, which is essential to the meaning of the sentence.
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