关键的

例句：

1. 1. The key to solving this problem lies in understanding the underlying causes.
   解决这个问题的关键在于理解其根本原因。
2. 2. This is the key to unlocking the door.
   这是打开这扇门的关键。
3. 3. The success of the project depends on meeting all the key requirements.
   项目的成功取决于满足所有关键要求。