Answer:
Option C, They have a closed circulatory system
Explanation:
Cephalopods belong to phylum Mollusca and are unique in sense that they have a closed circulatory system. This closed circulatory system consists of three unusual hearts with arteries, veins, and capillaries. Excepts Cephalopods, all majority of mollusks have open circulatory system. In open systems, heart pumps blood through blood vessels into the gills and then into body cavities (hemocoels)
Hence, option C is correct
