The correct option is
D Haemocyanin
Mollusca is coelomate. Hemocoel is the body cavity through which blood and coelomic fluid circulate. The blood contains a pigment known as haemocyanin. It helps to carry the oxygen throughout the body. They are suspended directly in the body fluid known as haemolymph. It appears blue. Oxygenation causes a color change between the colorless Cu(I) deoxygenated form and the blue Cu(II) oxygenated form.
So, the correct answer is option C.