题目选项分析

Commonly called spiral galaxies, disk

galaxies take form in the universe when

earlier, less flat, galaxies accumulate the mass of smaller nearby galaxies and rotate faster, thus flattening.

Commonly called spiral galaxies, disk

galaxies are formed in the universe, and when

earlier, less flat, galaxies accumulate the mass of smaller nearby galaxies and rotate faster, thus flattening.

题目基本信息

难度：难