The correct option is B hypersecretion of thyroxine
Exophthalmic goitre is an enlargement of the thyroid gland. Its typical feature is exophthalmos, i.e. bulging of the eyes. It occurs due to hyperthyroidism or hypersecretion of thyroxine.
Hyposecretion of thyroxine results in hypothyroidism, which reduces the basal metabolic rate of the body.
Thyrocalcitonin is also secreted by the thyroid gland, but it has no role in the basal metabolic rate. It helps in regulating blood calcium levels along with parathyroid hormone.