<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 68-year-old woman with osteoarthritis comes to the physician because of a swollen and painful right knee for the past 2 days. Temperature is 37C 98.6F. Examination shows erythema and swelling of the right knee with a normal range of motion. An x-ray of the right knee shows punctate radiodensities in both menisci and in the joint capsule. Arthrocentesis of the right knee joint yields 5 mL of cloudy fluid with a leukocyte count of 27,000mm3. Which of the following is the most likely underlying mechanism of this patients knee pain?? A: Calcium pyrophosphate dihydrate crystal deposition, B: Immune complex deposition, C: Noncaseating granuloma formation, D: Gram-negative diplococci infection, E: Monosodium urate crystal precipitation,  <response>: This is a patient with acute onset of a swollen, painful knee with evidence of inflammation erythema, swelling, elevated joint fluid leukocyte count and radiographic findings of punctate densities in the menisci and joint capsule. The key findings are the acute inflammation of the knee joint along with the radiographic evidence of punctate densities, which narrows the likely causes to crystal-induced arthritis vs septic arthritis. The elevated leukocyte count in the joint fluid makes infection a possibility, but the acuity of symptoms and lack of fever makes this less likely. The punctate densities on x-ray are classic for calcium pyrophosphate deposition disease CPPD, also known as pseudogout.Therefore, the most likely underlying mechanism is calcium pyrophosphate dihydrate crystal deposition.A: Calcium pyrophosphate dihydrate crystal deposition 