three distinct layers

例句：

1. 1. We need three people to finish theproject.
   我们需要三个人来完成这个项目。
2. 2. Thecompany has grown threefoldin the past five years.
   这家公司在过去五年里增长了三倍。
3. 3. Hehas three children, all of whom aretwins.
   他有三个孩子，都是双胞胎。