The correct answer is a - II, b - I, c - III, d - IV. Explanation & Key Takeaways: • The below table is correctly matched • +---------------------+---------------------+ | Respiratory Pigment | Animal/Animal group | +---------------------+---------------------+ | Haemoglobin | Vertebrates | | Chlorocruorin | Annelida | | Hemerythrin | Lingula | | Haemocyanin | Molluscs | +---------------------+---------------------+ Related Concepts: • Hemoglobin: • Haemoglobin is a respiratory pigment found in Vertebrates. • A hemoglobin (Hb) molecule is a conju­gated protein because it consists of a simple protein and with a non-protein part. • Chlorocruorin: • Chlorocruorin is a respiratory pigment found in Annelida. • It is a green-coloured respiratory pig­ment containing iron and is found in the plasma of some polychaetes (e.g., Serpulid, etc.). • Haemerythrin (Haemo-erythrin): • Hemerythrin is a respiratory pigment found in Lingula • It is an iron-containing respiratory pig­ment found in the blood corpuscles of some invertebrates (e.g., Sipunculans, etc). • It is pink or violet colored in the oxygenated state and colorless in the deoxygenated state • Haemocyanin: • Haemocyanin is a respiratory pigment found in Molluscs • A blue-green copper-containing respira­tory pigments found in some crustaceans. • Most molluscs and arthropods contain hemocyanin, such as the horseshoe crab and the giant octopus. • Haemocyanin works better than hemoglobin in lower oxygen environments like the bottom of oceans/seas.