Concept:Blood corpuscles include cells with different shapes; leucocytes are known for their irregular, amoeboid form.Explanation:Leucocytes, or white blood cells, can change shape and move like an amoeba.Erythrocytes are biconcave discs.Thrombocytes are small fragments, not true cells.Plasma is the liquid part of blood.Therefore, the irregular and amoeboid corpuscles are leucocytes.Answer:A. Leucocytes