Correct Answer: A

Rationale: The correct answer is Vitamin B12. Vitamin B12 deficiency can lead to megaloblastic anemia, a condition characterized by the production of abnormally large and immature red blood cells. Lower extremity paresthesias, such as tingling or numbness, are common neurological symptoms associated with vitamin B12 deficiency. Folate deficiency can also cause megaloblastic anemia but is not typically linked to lower extremity paresthesias. Iron deficiency leads to microcytic anemia, not megaloblastic anemia. Vitamin K deficiency is associated with bleeding tendencies, not megaloblastic anemia or paresthesias.

Correct Answer: B

Rationale: In this scenario, the rising lactic acid levels in a 65-year-old man after a coronary artery bypass graft could indicate bowel ischemia. Bowel ischemia can lead to anaerobic metabolism, causing an increase in lactic acid levels. Excessive sedation may cause respiratory depression but would not directly lead to rising lactic acid levels. Excessive volume infusion in the operating room might cause fluid overload but would not typically result in rising lactic acid levels. Mild hypothermia postoperatively could lead to shivering and increased oxygen consumption, but it is less likely to be the primary cause of rising lactic acid levels in this context.

Correct Answer: B

Rationale: The correct answer is B: Underexcretion of uric acid. In gouty arthritis, the crystallization within the synovial fluid of the affected joint is caused by the underexcretion of uric acid, leading to the accumulation and subsequent crystallization of urate crystals.
Choice A, destruction of proteoglycans, is incorrect as it is not directly related to the crystallization process in gouty arthritis.
Choice C, overexcretion of uric acid, is incorrect because gout is primarily associated with underexcretion or decreased excretion of uric acid rather than overexcretion.
Choice D, increased absorption of uric acid, is also incorrect as the primary issue in gouty arthritis is the body's inability to properly eliminate uric acid.

Correct Answer: B

Rationale: The correct answer is B: Immune complex deposition, increased capillary permeability, and cellular proliferation. Acute glomerulonephritis is characterized by inflammation of the glomeruli in the kidneys. This inflammation leads to the deposition of immune complexes, increased capillary permeability, and cellular proliferation, which collectively contribute to a decreased glomerular filtration rate.
Choice A is incorrect as decreased renal-induced constriction of the renal arteries would not directly result in decreased glomerular filtration rate.
Choice C is incorrect as necrosis of nephrons due to increased kidney interstitial hydrostatic pressure would affect kidney function differently.
Choice D is incorrect as scar tissue formation in the proximal convoluted tubule due to toxin-induced collagen synthesis is not a typical feature of acute glomerulonephritis.

Correct Answer: B

Rationale: The correct answer is 'Both an adult male with a history of alcoholism and a middle-aged male who smokes a pipe.' Alcohol consumption and tobacco use, such as smoking a pipe, are well-known risk factors for developing oral cancer. These two factors significantly increase the likelihood of developing oral cancer compared to the other choices. Taking oral contraceptives, eating spicy foods regularly, and chewing gum frequently are not established risk factors for oral cancer, making them less likely to lead to the development of this type of cancer.