Which of the following is a complication of hemophilia?

Answer B, Hemarthrosis, is correct. Hemophilia is a bleeding disorder where blood doesn't clot normally. Hemarthrosis, or bleeding into joints, is a common complication due to joint trauma. Hematuria (A) is blood in urine, not specific to hemophilia. Hemoptysis (C) is coughing up blood, more common in lung conditions. Hematemesis (D) is vomiting blood, seen in gastrointestinal issues. In hemophilia, bleeding into joints (hemarthrosis) is a key complication due to lack of clotting factors.