Correct Answer: A

Rationale: The correct answer is A: Respiratory acidosis. In respiratory acidosis, there is an accumulation of CO2 in the blood, leading to a decrease in pH. The elevated PaCO2 of 55 mmHg in the given results indicates hypoventilation, causing respiratory acidosis. Choices B, C, and D are incorrect because the provided data does not show metabolic acidosis, respiratory alkalosis, or metabolic alkalosis.

Correct Answer: B

Rationale: Disseminated intravascular coagulation (DIC) is characterized by simultaneous clotting and bleeding throughout the body. This imbalance in the body's clotting system leads to the formation of blood clots in small blood vessels, which can consume clotting factors and platelets, ultimately leading to excessive bleeding. Choices A, C, and D are incorrect because they do not describe the characteristic feature of DIC, which involves both clotting and bleeding.

Correct Answer: B

Rationale: The correct answer is B: Insufficient circulating blood volume. Hypovolemia is a condition characterized by a decrease in the volume of blood plasma. This reduction in circulating blood volume can lead to inadequate perfusion of tissues and organs, potentially resulting in shock if left untreated. Choices A, C, and D are incorrect because increased urine retention, bounding peripheral pulses, and crackles auscultated in the lungs are not typical manifestations of hypovolemia.

Correct Answer: A

Rationale: The correct answer is Parathyroid hormone (Choice A). Parathyroid hormone plays a key role in regulating calcium levels in the blood. When there is an imbalance in parathyroid hormone secretion, it can lead to increased calcium levels in the blood. Antidiuretic hormone (Choice B) is involved in regulating water balance, not calcium levels. Calcitonin (Choice C) helps lower blood calcium levels and is unlikely to cause an increase. Melatonin (Choice D) regulates sleep-wake cycles and does not have a direct effect on calcium levels in the blood.

Correct Answer: A

Rationale: The correct answer is A: Erythropoietin. The kidneys produce erythropoietin to stimulate the production of red blood cells. Insulin and glycogen are not hormones secreted by the kidneys; insulin is produced by the pancreas, and glycogen is a stored form of glucose. Testosterone is a hormone primarily produced by the testes in males and to a lesser extent in females. Thyroid stimulating hormone is produced by the pituitary gland to regulate thyroid function, not red blood cell production.