The correct option is A Haemocoelic
Haemocoelic system is a common system which helps in the process of respiration and circulation in many annelids. The blood vessels are represented by coelomic channels, filled with blood-like fluid called hemolymph. These channels form the haemocoelomic system. Exchange of gases takes place in these channels with the external environment through the process of difusion, mediated by the most skin of the leech.