There are a few ways to distinguish who said it: 1. Check the dialogue text: The text in the dialogue box is usually created by both parties in the dialogue, so you can check the dialogue text to determine who said it. In novels, the names of the two sides of the conversation or the names of the characters would usually be placed in the text so that one could infer who was speaking based on this information. 2. Check the context: Sometimes the content in the dialogue box is additional content or part of the dialogue, so you can check the context to determine who said it. In novels, the context of a conversation would usually be written together so that one could infer who was speaking based on the context. 3. Ask the dialogue participants: If you are not sure who said the content in the dialogue box, you can ask the dialogue participants. For example, if the content in the dialogue box was said by a certain character, they could ask if the character had appeared in the dialogue or if they knew the content in the dialogue box.