1.The existence of oil wells has been known for a long time.为什么用has 而不用have
问题描述：
1.The existence of oil wells has been known for a long time.为什么用has 而不用have
答
主语 existence
答
主语是The existence ，单数，所以用has
of oil wells 只是修饰成分
答
因为主语是 existence,是个抽象名词,所以谓语动词用 单三 has
答
因为作主语的是 existence