题目解析:
原文 Only a little heating will soften the ice and get the process started, allowing the rock and metal to sink to the center and the slushy ice to float to the surface.对应 B 选项。It is much easier for an icy body to differentiate than for a rocky one, since the melting temperature of ice is so low.对应 C 选项。Astronomers can tell that it lacks a dense core from the details of its gravitational pull on the Galileo spacecraft during several very close flybys. 对应 D 选项。所以选择 A 选项。