以下哪一种技术属于频谱多普勒技术
A．彩色M型
B．连续脉冲多普勒技术
C．彩色多普勒能量图
D．伪彩色编码二维显像
E．彩色多普勒血流显像
参考答案：B
单词拼写。
1. Trees along the road provide ____ (遮蔽) from the sun for the farmers.
2. As e____ was cut off, they had to use candles instead.
3. The poor man was badly i____ in the train accident.
4. The ____ (受到惊吓的) girl was speechless after she saw the terrible scene.
5. More than 90 percent of the houses were badly ____ (损坏) by the flood.
下列金属中，能做接触器触点材料的是（）。
A.铝
B.铅
C.铁
D.银
