outermost shell

例句：

1. 1. The outermostshell of the coral is made up ofcalcium carbonate.
   珊瑚的最外层壳由碳酸钙组成。
2. 2. The outermost shellof the sea turtle is a hard,protective covering.
   海龟的最外层壳是一种坚硬的保护性覆盖物。
3. 3. The outermost shell of the oyster isused for protection and to store food.
   牡蛎的最外层壳用于保护和储存食物。