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' 。
He agreed that a train did come into the station at the time on the paper and that it did stop, but only to take on mail, not passengers.
搬运工说,正如纸条所说,确有一趟火车在那个时刻到站,但它只停站装邮件,不载旅客。