In response to low levels of calcium, the parathyroid glands release a hormone that dissolves some of the calcium in the bones, moving it into the blood. this is an example of a) a positive feedback loop, because a condition in the body causes an increase in a hormone. b) a positive feedback loop, because the low level of calcium in the blood is returned to normal. c) a negative feedback loop, because increased calcium levels cause the parathyroid glands to release less hormone. d) a negative feedback loop, because the amount of calcium in bone decreases as a result of the parathyroid hormone. eliminate

the correct answer would be option C.

The secretion of the parathyroid gland is mainly regulated with the help of a negative feedback loop.

The decreased levels of calcium in the blood are sensed by calcium-sensing receptors present on the cells of the parathyroid gland.  

The parathyroid gland starts secreting the parathyroid hormone in response to this stimulus which results in the release of calcium present in bones reserves.

However, with the help of a negative feedback loop, the secretions of parathyroid gland are regulated to the normal level.  

In negative feedback, the increased amount of calcium in the blood results in the decreased amount of parathyroid hormone.