It is estimated that the number of foreigners coming to China to learn the language over the last few years ________ maintained an average annual growth rate of 35 percent．
A.hasB.haveC.isD.are在线课程A
这句句子的意思是“据估计，在过去的几年中，来中国学习语言的外国人以每年35％的年增长率递增。”这里有时间状语over the last few years，句子要用现在完成时，所以选项C和D均不对。而a number of加上可数名词复数，我们谓语动词用复数，the number of加上可数名词复数，谓语动词用单数，所以这里用has．