The correct answer is C. Hypotension, rapid weak pulse, and rapid respiratory rate.
Rationale:
Addisonian crisis, also known as acute adrenal insufficiency, is a life-threatening condition that occurs when the body does not produce enough cortisol and aldosterone due to adrenal gland dysfunction or damage. The main clinical manifestations of Addisonian crisis are related to the loss of fluid volume and electrolytes, which result in hypotension, rapid weak pulse, and rapid respiratory rate. Other common clinical manifestations include nausea, vomiting, abdominal pain, fever, and altered mental status.
Option A is incorrect because thin, fragile skin and ecchymoses are clinical manifestations of chronic adrenal insufficiency, not Addisonian crisis. Weight loss, not weight gain, is also a common manifestation of Addisonian crisis due to decreased appetite and catabolism.
Option B is incorrect because palpitations and diaphoresis are not typical clinical manifestations of Addisonian crisis.
Option D is incorrect because abrupt onset of hyperpyrexia (high fever), extreme tachycardia (fast heart rate), and delirium are not clinical manifestations of Addisonian crisis, but rather suggest a different medical condition, such as sepsis or hyperthyroidism.