none作主语指代三者或三者以上的可数名词复数时，谓语用单数也可用复数，常无多大区别；但当其意重于“每个都不”含义时，谓语用单数，当其意重于“所有都不”时，谓语用复数eg:None of them are the coaches he mentioned in his speech.(表示：他在他的演讲中不止提到一个教练）None of them is the coach he mentioned in his speech.（表示：他在他的演讲中只提到了一个教练）且本题中，后面用的是a good singer而不是good singers...
