Which of the Following Statements Regarding Ca²⁺ Homeostasis Is True

Which of the following statements regarding Ca²⁺ homeostasis is true?

A) Parathyroid hormone directly stimulates Ca²⁺ reabsorption by the kidneys.
B) Parathyroid hormone directly stimulates Ca²⁺ absorption from the GI tract.
C) In the absence of parathyroid hormone,plasma Ca²⁺ levels would be abnormally low,resulting in the hyperpolarization of nerve and muscle membranes.
D) When plasma Ca²⁺ increases above normal,the secretion of parathyroid hormone increases.
E) Vitamin D decreases the renal tubular reabsorption of Ca²⁺.