A. Colour blindness is a genetic disorder in which the affected individual can not distinguish between colours.
B. Simple goitre is the enlargement of thyroid gland which occurs due to deficiency of iodine in the body. Iodine is needed for the synthesis of thyroid hormone. When the iodine levels are low, thyroid gland becomes hyper active and enlarged to compensate the deficiency of thyroid hormone in the body. The enlarged thyroid gland is visible as a swelling in the throat known as goitre.
C. Ophthalmic goitre or exophthalmic goitre occurs due to over secretion of thyroid hormone. In exophthalmic goitre, protrusion of eyeballs occur due to deposition of excess fat behind the eyes.
Hence, deficiency of iodine in food or water leads to 'simple goitre'.