The correct option is B Leech
An open blood vascular system is the one which lacks a blood capillary system and only consists of a large cavity filled with blood called haemocoel. It is seen in memebers of the phylum arthropoda (e.g: silkworm), mollusca (e.g: squid) and echinodermata (e.g: starfish).
A closed blood vascular system has a blood capillary system and doesnt not have a haemocoel. It is seen in annelids (e.g : leech) and chordates.