Final answer:
The correct answer is (c) Patty Melt, which is a sandwich and a play on words, combining Charlie Brown's character with a food item.
Step-by-step explanation:
The correct answer to the question "Who is Charlie Brown's gal pal is a hamburger with Swiss cheese & onions served on grilled rye"? is (c) Patty Melt. This question is a play on words, combining a familiar character from the Peanuts comic strip with a popular sandwich. Charlie Brown's actual female friend from the comic strip is named Peppermint Patty, but a patty melt is a type of sandwich that includes a hamburger patty, Swiss cheese, and onions on grilled rye bread.