声明：逗号是一个开放的学习内容创作、分享与教学平台，以上内容（包括多媒体素材）为用户创建、编辑、上传和发布，本平台仅提供信息存储服务。

Disclaimer: The content above (including the multimedia materials if any) is created, uploaded and posted by users of Douhao. As an open creative platform, Douhao only provides information storage services.