配图应该放个莫比乌斯带，正即是反，反即是正。。。

来源: trivial 于 2022-04-17 08:34:24 [旧帖] [给我悄悄话] 本文已被阅读：次

WENXUECITY.COM does not represent or guarantee the truthfulness, accuracy, or reliability of any of communications posted by other users.