Whether a planet has an atmosphere or not depends on a number of factors: mass, temperature, composition of the crust, volcanic activity, and complex evolutionary processes.
rank the planets according to how well they retain their atmospheres, using the following criteria:
a. the planet that still maintains its primary atmosphere, ranks first.
b. the planet that lost its primary atmosphere but retains a dense secondary atmosphere, ranks second.
c. the planet that lost its primary atmosphere and retains a tenuous secondary atmosphere, ranks third.
d. the planet that retained neither its primary nor secondary atmospheres, ranks last.