Which of the Following Statements Regarding Ca²⁺ Homeostasis Is TRUE

Multiple Choice

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⁺.