During the rock cycle, cooling magma and lava from igneous rock, heat and pressure cause other rocks to turn into metamorphic rock, and weathered rock on the surface is eventually turned into sedimentary rock. Rocks move through this cycle at different rates, but it can take some rocks several billion years to complete the cycle. Using this information, what is the most likely reason why scientists use models to study the rock cycle? A. The rock cycle only affects objects that are too small to be observed directly.

B. The rock cycle is only an abstract idea and does not actually occur in nature.

C. The rock cycle no longer occurs on Earth.

D. The rock cycle takes too long to be able to observe it in entirety.