标题: 每天请教一道题! [打印本页] 作者: 龙o虾 时间: 2017-10-18 20:40 标题: 每天请教一道题! New theories propose that catastrophic impacts of asteroids and comets may have caused reversals in the Earth's magnetic field, the onset of ice ages, splitting apart continents 80 million years ago, and great volcanic eruptions.