Which of These Statement Does NOT Apply to Calcium Homeostasis

Multiple Choice

Which of these statement does NOT apply to calcium homeostasis

A) It involves immediate adjustments required to maintain a constant free Ca²⁺ concentration on a minute-to-minute basis.
B) It involves slowly responding adjustments required to maintain a constant total amount of Ca²⁺ in the body.
C) It is maintained primarily by the actions of parathyroid hormone.
D) Calcium level in blood may be lowered by the action of calcitonin.