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' 。
There is always hope that in its labyrinth of musty, dark, disordered rooms a real rarity will be found amongst the piles of assorted junk that little the floors.
人们还常常有希望在发霉、阴暗、杂乱无章、迷宫般的店堂里,从杂乱地摆放在地面上的、一堆堆各式各样的破烂货里找到一件稀世珍品。