15 minutes做主语时,谓语动词用单数.这是要遵循主谓一致的原则,详细见如下解释,
表示时间、距离、度量、重量、金额等的复数名词作主语,被看作整体时,谓语动词用单数;若强调个体也可以复数.如:
Twenty years is a long time.
二十年是很长时间.
Two kilometers is a long way to go on foot.
步行两千米是一段很长的路程.
Six months have passed,and we still have no news of them.
六个月过去了,我们依然没有他们的消息.
比较:
Ten dollars is too much for this old coin.
这个古币没有10块钱这么高的价格.
Three dollars were paid for the old coin.
那个古钱花了3块钱.
Twenty years is a long time.
20年是一段很长的时间.
Twenty years have passed since they got married.
他们结婚已有20年了.