Prepare with purpose.
Perform with confidence.

By definition, VC = IRV + TV + ERV. Rearranging: ERV = VC - (IRV + TV) = 5000 - (3000 + 500) = 1500 mL = 1.5 L. - B, D, E give incorrect arithmetic values. - C 3.5 L exceeds the given VC components.

In pregnancy, diagnosis of HSIL still requires histology, but procedures that risk pregnancy loss (e.g., endocervical curettage, cone biopsy) are avoided unless invasive cancer is strongly suspected. Colposcopy-directed punch biopsy of abnormal areas is safe and adequate for histologic confirmation. - A repeating cytology does not provide histologic grading or rule out invasion. - B endocervical curettage is contraindicated in pregnancy due to risk of membrane rupture/bleeding. - D cone biopsy carries higher obstetric risk and is reserved when invasion cannot be excluded on punch biopsy/colposcopy. - E hysterectomy is treatment for confirmed invasive disease, not for initial tissue diagnosis in a stable 18-week pregnancy.

Porphyria cutanea tarda (PCT), the most common porphyria, is due to uroporphyrinogen decarboxylase deficiency, leading to accumulation of uroporphyrin, which causes tea-colored urine and photosensitivity with blistering skin lesions on sun-exposed areas. It is often associated with hepatitis C, HIV, or alcohol use. - B ALA dehydratase deficiency causes a rare form of porphyria presenting with neurovisceral symptoms, not classic blistering photosensitivity. - C Porphobilinogen deaminase deficiency causes acute intermittent porphyria (5 P's: Painful abdomen, Port-wine urine, Polyneuropathy, Psychological disturbances, Precipitated by drugs). - D Ferrochelatase deficiency leads to erythropoietic protoporphyria with childhood photosensitivity and protoporphyrin accumulation. - E ALA synthase is the rate-limiting enzyme upregulated by barbiturates and downregulated by heme.

Hookworms (e.g., Ancylostoma duodenale, Necator americanus) attach to the intestinal mucosa and cause chronic blood loss and iron-deficiency microcytic anemia. First-line therapy for most intestinal nematodes (including hookworm, Ascaris, Enterobius) is a benzimidazole such as mebendazole or albendazole, which inhibits microtubule polymerization and depletes parasite glucose stores. - A Metronidazole is used for protozoa (e.g., Entamoeba histolytica, Giardia, Trichomonas) and some anaerobic bacteria, not hookworms. - C Levamisole is an older antihelminthic largely obsolete due to toxicity. - D Ivermectin is preferred for Strongyloides and onchocerciasis, not first-line for hookworm. - E Niclosamide is used mainly for cestodes (tapeworms).

At rest, O₂ and CO₂ are perfusion-limited: they equilibrate between alveolar air and capillary blood early along the capillary; total transfer is limited by blood flow. With slower blood flow, each RBC spends more time in the capillary, but O₂ still equilibrates and its uptake is primarily increased by improving perfusion. The classic teaching in exam questions is that O₂ is perfusion-limited under normal conditions. - A, D N₂ and helium are essentially inert, not significantly taken up by blood. - C CO₂ is also perfusion-limited but far more soluble; the question stem usually points to O₂. - E CO classically is diffusion-limited, not perfusion-limited.