Which one of the following statements regarding the Earth's outer core is best supported by information presented in the passage? A. Heat circulation in the outer core controls the growth and diminution of the polar ice caps. B. Impact of asteroids on the Earth's surface alters the way in which the outer core vents its heat into the mantle. C. Motion of electrons within the metallic fluid in the outer core produces the Earth's magnetic field. D. Friction and turbulence near the boundary between the outer core and the mantle are typically caused by asteroid impacts. E. Cessation of heat circulation within the outer core brings on multiple reversals in the Earth's magnetic field.