The most common bacterium causing joint pain . . . . . . . .

Answer: Option A

The most common bacterium causing joint pain is Brucella.
Brucellosis is a disease you get from the bacteria Brucella. You get brucellosis from drinking unpasteurized milk, eating unpasteurized milk products or handling infected animals.
Symptoms can come and go for a long time and include fever, joint pain and sweating. Brucellosis is treated with antibiotics.