dark stage

例句：

1. 1.The dark stage of the disease is when symptoms first appear.
   疾病的暗阶段是症状首次出现的时候。
2. 2. During the dark stage, the team worked tirelessly to find a solution.
   在暗阶段，团队努力不懈地寻找解决方案。
3. 3.The dark stage of the project was marked by intense collaboration and communication.
   项目暗阶段以激烈的合作和沟通为标志。