Sc has more gas so Sa galaxies can't form any more stars.
One of these does not describe an elliptical galaxy:
a-They contain primarily low-mass stars owing to lack of recent star formation.
b-They have a smooth light distribution with various degrees of flattening compared to a circular shape.
c- They cover the widest range of masses, from the smallest to the largest galaxies in the universe.
d- They have a central bulge and a disk, but no spiral arms.