Not until about 2000 BC________________________done.

A．were known of the oldest paintings

B．the oldest of known paintings were

C．the oldest known were painting

D．were the oldest known paintings

CT窗口技术的概念，错误的是（）

A.目前，CT数字图像的灰阶大都为12个比特

B.在限定的范围内，显示诊断所需感兴趣区信息的方法，被称之为数字图像中的窗口技术或窗宽、窗位调节

C.窗宽和窗位的调节属于数字图像处理技术，它能抑制或去除噪声

D.窗宽和窗位的调节属于数字图像处理技术，它能增加图像的信息

E.窗宽增大，图像对比度降低，窗宽减小则图像对比度增高