If you don't know a person's last name, use 'ma'am' or 'sir'.
如果你不知道一人的姓, 你应称呼他为 'ma'am' 或 'sir' 。
Twenty or thirty pages of information handed to any of the major world powers around the year 1925 would have been sufficient to change the course of world history.
如果把二三十页的情报交给1952年前后的任何一个世界强国,就足以改变世界历史的进程。