Which of the following best describes a comet’s motion?
a. they stay in relatively the same place until they fade from sight.
b. they are in constant motion until they fade from sight.
c. they are in constant motion until they reach earth.
d. they are in constant rotation around the sun until they form stars.

Comets are celestial bodies constituted by ice, dust and rocks that orbit around the Sun, after having been altered by the Oort cloud; following different trajectories that can be highly eccentric elliptical (periodic trajectories), parabolic or hyperbolic.

One of the main characteristics of a comet is that it travels quite fast, on its way around the Sun and has a long tail. It should be noted that the tails of comets always go in the opposite direction to the Sun (due to the radiation pressure of sunlight).