What Is Believed to Be the Origin of Giant Elliptical

Multiple Choice

What is believed to be the origin of giant elliptical galaxies?

A) Giant elliptical galaxies formed as such and have remained unchanged ever since.
B) Giant elliptical galaxies grew by devouring smaller galaxies.
C) Collisions of galaxies in the cluster produce a smooth distribution of stars through the cluster, which sink to the center of the cluster and form giant galaxies.
D) Giant elliptical galaxies have grown continuously since their formation by accretion of intergalactic gas.