Which of these activities will most likely impose an external cost? an athlete works out at a gym. a young mother pushes her baby in a stroller. a secretary smokes a cigarette in a crowded break room. a construction worker eats a hotdog during his lunch break?

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.