天然的可能很少吧。工業用的肯定都是人造的。

來源: mapell22 於 2014-08-25 16:30:03 [博客] [舊帖] [給我悄悄話] 本文已被閱讀：次

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