调节“彩超”中的速度标尺及滤波范围，下列哪项是不正确的（）
A.高速血流选择高速标尺
B.低速血流选择低速标尺
C.消除低频信号干扰，应采用高速标尺
D.低通道滤波适合检查低速血流
E.高通道滤波适合检查高速血流
参考答案：C
解析：彩色多普勒技术中速度标尺的调节应注意须与被检测的血流速度相匹配，对腹部及外周血管一般用低速标尺，对心血管系统应用高速标尺。滤波器的调节应注意对低速血流用低通滤波，以防止低速血流被"切除"，对高速血流用高通滤波，以去除低频运动信号的干扰。
When I was a small child，during the war，we were very poor and we lived in a faraway village.One day，on the road，I found the ____ pieces of a mirror.There was a motorcycle accident. I ____ to find all the pieces and put them ____，but it was not possible，so I used only the ___ piece and I made it round.I could ____ with it as a toy and became greatly attracted by the ____ that I could reflect light to dark places where the sun would never shine—in ____ holes and some other dark places.It became a game for me to ____ light into the darkest places I could find. I ____ the little mirror，and，as I grew up，I would take it out ____ I had nothing to do and ____ the game.As I became a man，I grew to realize that this was not ____ a child’s game but a metaphor(暗喻) for what I might ____ my life.I came to ____ that I am not the light or the source of light.But light—truth，understanding，knowledge—is there，and it will shine in many dark places ____ I reflect it. I am just a single piece of a mirror whose ____ design and shape I do not know.___，with what I have I can reflect light into the dark places of this ____—into the black places in the ____ of men—and change some things in some people.Perhaps others may see and do the same.This is what I am about.This is the ____ of my life.
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