Which of the following does not belong in the definition of matter?

Matter is defined by its fundamental properties, which include having mass and occupying space. These properties are essential in distinguishing matter from other entities. While matter can contain energy in various forms, such as kinetic or potential energy, this is not a defining characteristic of matter itself.

The idea that matter can "travel at the speed of light" is not aligned with the principles of physics regarding matter. According to the theory of relativity, only massless particles, such as photons, can travel at light speed. All matter has mass and thus cannot reach this speed. Therefore, saying that traveling at the speed of light is a defining characteristic of matter does not fit within the established understanding of what matter is. This distinction helps clarify that options related to mass, space, and energy are inherently linked to matter, while the notion of traveling at the speed of light does not pertain to its definition.