More precisely, the server responds with either 300 Multiple Choices or 406 Not Acceptable (when server-driven, user-agent provided acceptance criteria is provided but the server cannot automatically make a selection).
更具体来说，服务器响应300 Multiple Choices或406 Not Acceptable（当服务器驱动时，用户代理提供了接受标准但服务器无法自动选择时）。