Which of the following best describes kinetic molecular theory?

Kinetic molecular theory posits that all particles of matter (atoms and molecules) are in constant motion. This motion varies depending on the state of matter: solids, liquids, and gases differ in how freely their particles can move. In solids, particles vibrate in fixed positions; in liquids, they can slide past each other while still being close together; in gases, the particles move freely and rapidly, filling the available space. The core idea of kinetic molecular theory is the understanding that this constant motion of particles is fundamental to explaining the behavior of matter at the molecular level. Therefore, stating that all particles are in constant motion accurately captures the essence of kinetic molecular theory.