There is no doubt, in my opinion, matters is not the speed, but the quality of the product.
A. what what
B. that that
C. that if
D. that what
网友回答
A. what what
B. that that
C. that if
(答案→)D. that what
解析：that引导一个同位语从句，在这个同位语从句中又有一个主语从句：what matters。句意：依我看，毫无疑问，重要的不是速度，而是产品的质量。