secret channel

例句：

1. 1.The secret channel is used to communicate with people in other countries.
   这个秘密通道被用来与其他国家的人进行沟通。
2. 2.The government has been using this secret channel to communicate with the opposition.
   政府一直使用这个秘密通道与反对派沟通。
3. 3. The secret channel was discovered by a team of scientists who were investigating a mysterious disappearance.
   一个科学家团队发现了这个秘密通道，他们正在调查一个神秘的失踪事件。