Answer:
The sentence that is correctly punctuated is the following one: "Let's get going," Ginnie shouted, "it's getting dark!"
Explanation:
The sentence above is a direct quotation. Quotation marks are for when you want to include someone else's words in your own writing. What is more, direct quotations contain a quote in which you report the exact words used.
In this case, the quote has been split. When you split a quote to introduce a parenthetical, you shouldn't capitalize the second part of the quote example: (it's getting dark!"). Also, the exclamation mark goes inside the quote because it applies to the quoted material, not to the whole sentence. For these reasons, the sentence chosen is the one that is correctly punctuated.