In which of the following sentences is hyperbole used?

Hyperbole is a figure of speech that involves exaggerated statements or claims that are not meant to be taken literally, used for emphasis or effect. The sentence, "I have a million things to do today," is a clear example of hyperbole. It emphasizes the feeling of being overwhelmed by a long to-do list by exaggerating the number of tasks to an impossibly high number.

In contrast, the other sentences convey straightforward information without exaggeration. "It was a sunny day" simply states a fact about the weather, "The cat sat on the mat" describes a specific action involving a cat and a mat without any overstatement, and "He ran quickly" provides a basic description of someone's speed, again without any hyperbolic element.