Correct Answer: A

Rationale: Anaphylaxis is a classic example of a Type 1 hypersensitivity reaction. In Type 1 hypersensitivity, allergens trigger an immediate immune response mediated by IgE antibodies, leading to the release of histamine and other mediators. This reaction can result in symptoms ranging from mild itching and hives to severe conditions like anaphylaxis, which is a life-threatening emergency. The other options, such as indigestion (choice B), beta cell destruction (choice C), and ABO transfusion reaction (choice D), are not classified as Type 1 hypersensitivity reactions. Indigestion is typically related to gastrointestinal disturbances, beta cell destruction is associated with autoimmune conditions like type 1 diabetes, and ABO transfusion reaction involves antibodies targeting incompatible blood groups, which is a different immune mechanism compared to Type 1 hypersensitivity.

Correct Answer: C

Rationale: The correct answer is C. In emphysema, impaired oxygenation results from enlarged and permanently inflated alveoli, leading to reduced surface area for gas exchange. Choices A, B, and D are incorrect. In emphysema, bronchioles are not typically filled with mucus, alveoli losing surfactant and collapsing is more characteristic of conditions like atelectasis, and purulent fluid accumulation in the bronchioles is commonly seen in conditions like pneumonia, not emphysema.

Correct Answer: A

Rationale: Polycythemia Vera, characterized by excess red blood cells, can cause tissue ischemia and necrosis due to the increased blood viscosity. This condition restricts blood flow, leading to inadequate oxygen delivery to tissues and subsequent tissue damage. Choices B, C, and D are incorrect because they are not directly associated with the pathophysiology of Polycythemia Vera.

Correct Answer: D

Rationale: The correct answer is D. Spinal cord injuries commonly occur due to hyperextension, hyperflexion, and compression. Hyperextension and hyperflexion refer to the excessive bending or stretching of the spinal cord, while compression is the exertion of pressure on the spinal cord. These mechanisms can lead to damage such as contusions, lacerations, and compression of the spinal cord. Choices A, B, and C are incorrect as they do not accurately represent the major mechanisms of spinal cord injuries.

Correct Answer: B

Rationale: The correct answer is B: T cell deficiency. The symptoms described in the case, including low-set ears, a fish-shaped mouth, involuntary rapid muscular contraction, and decreased calcium levels, are indicative of DiGeorge syndrome. This syndrome is characterized by T cell deficiency due to thymic hypoplasia. B cell deficiency (Choice A), combined immunodeficiency (Choice C), and complement deficiency (Choice D) do not align with the clinical presentation and laboratory findings provided in the case. Therefore, T cell deficiency is the most likely diagnosis in this scenario.