FCN

例句：

1. 1. FCN stands for "First Class Network".
   FCN代表“一级网络”。
2. 2.The FCN is responsible for maintaining the network's security.
   FCN负责维护网络的安全。
3. 3. FCN is a popular online platform for learning and sharing knowledge.
   FCN是一个受欢迎的在线学习和知识分享平台。