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' 。
It is six o'clock.In the evening, the children usually do their homework, but this evening, they are not doing their homework.
现在是6点钟。晚上,孩子们通常是做作业,而今天晚上,他们没做企业。