There is no doubt，in my opinion， matters is not the speed，but the quality of the product.
A. that
B. which
C. what that
D. that what
网友回答
A. that
B. which
C. what that
(答案→)D. that what
解析：考查同位语从句和主语从句：句意：在我看来，毫无疑问，重要的是不是速度。而是产品的质量。Doubt后面是同位语从句，用that连接，说明doubt的内容。在同位语从句中is前面是主语从句，缺少主语，用what连接。选D。