Notice that the shoulder and hip bones are much larger and stronger in the frog (left) skeleton than in the perch (right) skeleton. Why do you suppose this is

the answer is b.) hydrogen bonds between bases.

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.