The answer is true because a monologue is basically just another word for a speech, and a dialogue is always just a coversation between two or more people. Bonus fact, a soliloquy is when someone is doing a monologue but they are the only ones on the stage.
Maybe when the writer uses italics in their righting, or if a character is saying something, they show the tone. If context could help, pay attention to that :)
