How Do We Explain the Relatively Low Mass of Mars

Multiple Choice

How do we explain the relatively low mass of Mars, which is much smaller than Earth or Venus?

A) Mars was fully formed in the outer regions of the solar system and migrated inward to its present orbit well after most planetesimals had disappeared. Thus, it did not grow further.
B) Mars was flung out of the still-molten Earth.
C) The early migration of Jupiter to the present location of Mars's orbit cleared away the planetesimals, which might have enlarged Mars after it formed somewhat later.
D) At some time early in the solar system, Mars and Jupiter exchanged orbits-after Jupiter had already swept up all the planet-building materials from Mars's present orbit.