In some molluscs,the free-swimming larva is a trochophore while in others,it is a veliger with the beginnings of a foot,shell and mantle.What is the relationship of these molluscan juvenile stages?

A)A veliger is found strictly in terrestrial molluscs
B)The trochophore is considered ancestral and the veliger is a derived larval stage
C)The two larval forms represent two early and distinct branches of molluscs
D)The veliger is ancestral and the trochophore is a derived larval stage
E)Only the cephalopods have the veliger stage;all other molluscs have a trochophore stage