Here's why:
* Clarity: Placing quotes inside commas makes it clear that the quoted phrase is part of the sentence and not a separate thought.
* Grammar: Commas are used to separate elements in a sentence, and the quotes should be treated as part of the element being separated.
Examples:
* Correct: "I'm going to the store," she said.
* Incorrect: "I'm going to the store", she said.
Let me know if you have any other grammar questions!