The correct answer is C. Understatement
Step-by-step explanation:
In writing and speaking, understatement is a figure of speech or device used to represent a situation, idea or similar in a way that this seems less important or intense than it really is, which is commonly use to intentionally reduce the significance or importance of some situation. Considering this, saying that you are "sad" if you are really miserable is an example of understatement because in this words are used to reduce the importance and intensity of a feeling or to show a situation is not as important as it really is which occurs in understatement.