— What do you think of Jeremy Shu-How Lin's overnight success?  

— I think it is not good luck but hard work _____ has made him what he is today. [ ]

A. that            

B. which            

C. when          

D. where

下列有关图像颜色子采样的叙述，不正确的是 ( ) 。

A．颜色子采样对亮度信号和色差信号分别采用不同的采样频率

B．颜色子采样方法是指对亮度信号的采样频率比对色差信号的采样频率低

C． MPEG-1和MPEG-2中都使用了4:2:0的子采样格式

D．若4:2:0子采样格式的分量量化精度为8位，则平均每像素数据量为12位