The Bekenstein entropy is proportional to the black hole mass squared; because the Schwarzschild radius is proportional to the mass, the Bekenstein entropy is proportional to the black hole's surface area. In fact,
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11D supergravity contains a 3-form field C. It also contains an electric 2-brane (M2) and a magnetic 5-brane (M5) under C. These branes are BPS states and they are also black branes.