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' 。
When you place a sheet of paper in a fax machine, the machine reads the writing on the page and changes the shapes of letters into electronic signals.
当你把一张纸放进传真机里,机器就会"读"纸上的字迹,把字的形状变为电子符号。