_______ is a respiratory infection in which fluid or exudate fills the alveoli, impairing gas exchange and causing symptoms such as productive cough, dyspnea, and fever.

A. Melasma is incorrect because melasma is characterized by dark, hyperpigmented patches on the skin, usually on the face, due to increased melanin production. It is often related to hormonal changes or sun exposure and does not involve a lack of pigmentation or white hair.

B. Vitiligo is incorrect because vitiligo involves patchy loss of skin pigmentation due to autoimmune destruction of melanocytes. Hair may be affected locally in the depigmented patches, but the condition does not typically result in generalized white hair or the reduced eye pigmentation seen in albinism.

C. Albinism is correct because it is a genetic condition characterized by a congenital lack of melanin, resulting in very light or white skin, white or very light hair, and reduced or absent pigmentation in the eyes. This lack of melanin also increases sensitivity to UV radiation and can affect vision.

D. Psoriasis is incorrect because psoriasis is a chronic autoimmune skin condition that causes red, scaly, and inflamed patches of skin. It does not affect hair color or eye pigmentation and is unrelated to melanin production.

A. High-grade daytime fever is incorrect because TB typically presents with a low-grade fever that is more pronounced in the late afternoon or evening. Night sweats are a classic symptom of TB and reflect the body’s immune response to the persistent infection, rather than a high fever during the day. High daytime fevers are more characteristic of acute bacterial infections, not the chronic course seen in TB.

B. Weight gain is incorrect because individuals with active TB often experience weight loss. Chronic infection increases metabolic demands, and the infection itself can suppress appetite, leading to progressive wasting and muscle loss. Weight gain would be unusual in the context of active TB.

C. Blood-tinged sputum is correct because active pulmonary TB can cause cavitation of lung tissue, where necrotic lesions erode into pulmonary blood vessels. This results in hemoptysis, which may range from small streaks of blood in sputum to more significant bleeding. Hemoptysis is a hallmark of active TB and often signals advanced disease or tissue destruction. Other accompanying respiratory symptoms include persistent cough, chest pain, and shortness of breath, reflecting inflammation and airway involvement.

D. Increased appetite is incorrect because TB typically causes anorexia, a loss of appetite, as part of the systemic effects of chronic infection. Reduced food intake, combined with increased metabolic demands and catabolism due to the infection, contributes to weight loss and fatigue.