Final answer:
The correct sentence is A. "When I was seven, my sister and I went to summer camp in Arkansas." This is because it properly uses a comma to separate the introductory phrase from the main clause.
Step-by-step explanation:
The correction that would best edit sentence 1 is A. When adding commas to a sentence, we typically use them to separate clauses or items in a list or to add a non-essential clause or phrase. The corrected sentence: "When I was seven, my sister and I went to summer camp in Arkansas." includes the necessary comma after the introductory phrase to clarify the sentence structure. Options B and C add unnecessary commas which can create confusion.
Commas are crucial for clear communication in writing. Their correct use helps to ensure the reader understands the writer's intended meaning by indicating pauses and separating ideas or elements within a sentence. This is why in sentence A, the comma is placed after the dependent clause "When I was seven", setting the stage for the main action in the sentence which is the trip to summer camp.