A Key Difference Between Bivalves and Gastropods Is That

A key difference between bivalves and gastropods is that

A) bivalves have a one-part shell, gastropods have a two-part shell.
B) bivalves take in food through an incurrent siphon, gastropods filter food with their gills.
C) bivalves are found only in marine environments, gastropods only occur in freshwater.
D) all bivalves have a shell, not all gastropods have a shell.
E) bivalves move by means of a muscular foot, gastropods move by via ciliated gills.