Thrombocytopenia:

Choice A reason: Increased glucose use doesn’t occur in DKA; insulin deficiency reduces glucose uptake. Fluid shifts are due to osmotic diuresis, not intravascular to intracellular movement, so this is incorrect for DKA’s mechanism.

Choice B reason: DKA involves metabolic, not respiratory, acidosis from ketones. Protein catabolism occurs, but fatty acid use and ketogenesis are primary, leading to acidosis and diuresis, so this is incorrect.

Choice C reason: Increased glucose and fatty acids contribute, but the mechanism is decreased glucose use causing ketogenesis. This option omits ketogenesis, a key DKA feature, so it’s less precise and incorrect.

Choice D reason: Insulin deficiency in DKA reduces glucose use, leading to fatty acid breakdown, ketogenesis, metabolic acidosis (pH 7.2), and osmotic diuresis (electrolyte loss). This fully explains the lab values, making it correct.

Choice A reason: A fracture is a break in the bone, as seen in the patient, but osteosarcoma is the underlying tumor causing the pathological fracture. Defining osteosarcoma as a fracture ignores its neoplastic nature, making this incorrect.

Choice B reason: A bone infection, or osteomyelitis, involves bacterial or fungal invasion, causing pain and inflammation. Osteosarcoma is a primary bone cancer, not an infection, with distinct histopathological features, making this an incorrect definition.

Choice C reason: Osteosarcoma is a malignant bone tumor, typically arising in long bones like the humerus, often causing pain, swelling, and pathological fractures. This matches the patient’s imaging findings and clinical presentation, making this the correct definition.

Choice D reason: A benign bone tumor, like an osteoma, does not metastasize or cause aggressive destruction. Osteosarcoma’s malignant nature leads to local invasion and potential metastasis, as implied by the fracture, making this incorrect.