题目选项分析

Atmospheres on planets within the habitable zone, the shell-shaped region of space surrounding a star within which a planet could maintain liquid water on its surface, rather than on more distant stars, are much more likely to harbor multicellular life when they contain water.

Planets within the habitable zone, the shell-shaped region of space surrounding a star within which a planet could maintain liquid water on its surface, are much more likely than more distant planets to harbor atmospheres which contain water and, possibly, multicellular life.