【正确答案】 A

【答案解析】[听力原文]
   At mission control, celebrations of a direct hit followed by first images of a huge dust cloud, evidence of success of the unmanned Deep Impact space probe after it slammed into the massive comet. While scientists at NASA's Jet Propulsion Lab look for the crater carved at impact, members of the observation team tell CNN, this comet, called Tempel 1, roughly half the size of Manhattan is not a threat to Earth. Its orbit is beyond Mars, about 83 million miles away. But we asked the head of NASA's Near Earth Object Program how many comets or asteroids are out there that could potentially threaten Earth.
根据新闻可知，Tempel 1是彗星。故选A。