An example of a change in a person's daily routine is:

Sleeping much later than usual is a definitive change in a person's daily routine because it directly impacts their schedule and activities during the day. A daily routine typically consists of consistent patterns of behavior related to time management, such as wake-up times, meal times, and various daily activities. When someone alters this pattern by sleeping later, it affects not only the duration of their sleep but also how they structure the rest of their day. This change can lead to impacts on productivity, social interactions, and even mood.

The other options indicate changes in behavior or emotional states, but they do not necessarily represent shifts in the established routine. Being aggressive, speaking less, or feeling mad pertains more to emotional responses and behaviors rather than a systematic alteration of one's daily activities or schedule. Therefore, these behaviors may manifest in a person's life without truly changing how they manage their day-to-day experiences.