外皮的

例句：

1. 1. The tree's bark is the outer layer of its skin.
   树的树皮是它的外层皮肤。
2. 2. The outer layer of the planet is composed of rocks and minerals.
   行星的外层由岩石和矿物质组成。
3. 3. The outer space is vast and unexplored.
   外太空广阔且未被探索。