题目

Astronomers (天文学家) say they are on the point of finding planets like Earth orbiting other stars, which is a key step in determining if we are alone in the universe. A top NASA official and other leading scientists say that within four or five years they should discover the first Earth-like planet where life could develop, or may have already. A planet close to the size of Earth could even be found sometime this year. At the annual American Astronomical Society conference this week, each discovery involving  so-called “exoplanets” —those outside our solar system — poin读中国某地区局部图，完成图中河流P的补给主要来自                                                A．地下水和雨水           B．冰川融水和雨水C．雨水与湖泊水           D．冰川融水与地下水