Which statement most accurately describes Megaloblastic anaemia?

A. A rapid severe systemic hypersensitivity reaction that may compromise airway, breathing or circulation. B. Obstruction of pulmonary arteries, commonly by thrombus originating in deep veins. C. A chronic inflammatory airway disorder with variable and usually reversible airflow obstruction. D. A macrocytic anaemia caused by impaired DNA synthesis, often from folate or vitamin B12 deficiency.