Which of the following is not a characteristic feature of phylum mollusca?
A. They are bilaterally symmetrical, triploblastic and coelomate animals
B. Unsegmented animals
C. They are usually dioecious and oviparous with indirect development
D. Respiratory organs are feather like gills in all molluscs and are present in the visceral hump, help in respiration and exretion.