Which of the following statements about the two models of solar activity, as they are described in the passage, is accurate? A. In both models cyclical solar activity is regarded as a long-lived feature of the Sun, persisting with little change over billions of years. B. In both models the solar-activity cycle is hypothesized as being dependent on the large-scale solar magnetic field. C. In one model the Sun's magnetic field is thought to play a role in causing solar activity, whereas in the other model it is not. D. In one model solar activity is presumed to be unrelated to terrestrial phenomena, whereas in the other model solar activity is thought to have observable effects on the Earth. E. In one model cycles of solar activity with Periodicities longer than a few decades are considered to be impossible, whereas in the other model such cycles are predicted.