Final answer:
The statement that Earth's crust is divided into rigid plates that move slowly is true. Plate tectonics theory explains the movement and interaction of these plates, which shape the Earth's surface and act as a planet's cooling system.
Step-by-step explanation:
The theory that the Earth's crust is broken into rigid plates that move slowly is indeed true. The Earth's lithosphere, composed of the crust and the uppermost rigid part of the mantle, is divided into tectonic plates. These plates move on the more fluid asthenosphere beneath them due to mantle convection and the movement is similar to the rate of growth of human fingernails. This movement can lead to continental drift, the creation of geological features such as mountains, and the occurrence of seismic activity. One of the most vital aspects of plate tectonics is its role in Earth's cooling system, allowing heat from the inner Earth to escape to space.