The key difference between the larger or "regular" moons and the smaller or "irregular" moons of the Jovian planets is that.
A) The larger moons are subjected to intense tidal forces, while the smaller moons are not.
B) The larger moons are massive enough to have been formed into a spherical shape by gravity.
C) The larger moons represent captured asteroids, while the smaller moons were formed in orbit about their host planet.
D) The larger moons have liquid water under their surfaces, while the smaller moons do not.
E) The larger moons have atmospheres, while the smaller moons do not.