If you know a man's last name, address him as 'Mr.'.
如果你知道一个男性的姓, 应该用 'Mr。' 来称呼他。
He was absent yesterday. Do you know why?
昨天他没到,你知道为什么吗?
Knowing that the industrious ant lives in a highly organized society does nothing to prevent us from being filled with revulsion when we find hordes of them crawling over a carefully prepared picnic lunch.