Vitamin d a. is essential for oxygen delivery to tissues b. deficiency causes parathyroid hormone levels to drop c. blood levels among adolescents have declined in recent years. d. in excess blocks absorption of calcium from the gi tract. e. none of the above

Vitamin D plays a vital role in the regulation of calcium deposits and maintenance of the phosphorous levels in the blood which are two elements that are significantly important for maintaining healthy bones.

The human body needs vitamin D to absorb calcium in the intestines and to recover calcium that would otherwise be excreted through the kidneys. It also essential for the development and strengthening of bones and it blocks the release of parathyroid hormones.

The answer would be letter E. None of the above

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