Lava that hardens on the surface is called an extrusion. The rock layers below an extrusion are always older than the extrusion. ... There, the magma cools and hardens into a mass of igneous rock called an intrusion. An intrusion is always younger than the rock layers around and beneath it.
<span>D. can grow as the animal grows. Endoskeleton is an internal skeletal system that provides a framework for the body. Unlike an exoskeleton, it grows as the body grows. </span>Humans, birds, fish and mammals have endoskeletons.
Heart......................
