Which of the following features are correct? Choose correct option. a. Graves' disease is a form of hyperthyroidism. b. Exophthalmic goitre is characterized by protrusion of the eyeballs. c. Hypothyroidism during pregnancy causes defective development and maturation of the growing baby. d. Deficiency of iodine in our diet results in hypothyroidism and enlargement of the thyroid gland.