3characteristics of carbon that allow it to be considered the backbone

The carbon has 4 valence electrons ( can have four bonds ) that allow it to form bonds and takes 4 hydrogen atoms to become saturated. I cannot come up with a 3rd characteristic

imagine a line passing through the center of earth that goes through both the north pole and the south pole. this imaginary line is called an axis. earth spins around its axis, just as a top spins around its spindle. this spinning movement is called earth's rotation. at the same time that the earth spins on its axis, it also orbits, or revolves around the sun. this movement is called revolution.