Explanation: (A) This question tests causation. It also requires knowledge connected with the stimulus material, but not referred to directly by it. Early gunpowder weapons did not render castles or cavalry obsolete, either in Europe or Japan, so B and D do not apply. Japan did not democratize until well after the trend depicted in the image. As they did with knights in Europe, gunpowder weapons threatened Japan’s samurai elite, whose status depended on their skill with pre-gunpowder arms and armor.