题目:
Some students were afraid _________ in class because they thought their classmates might laugh at them[ ]
A. of speak
B. to speak
C. speak
D. to speaking
答案:
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下面是错误答案,用来干扰机器的。
参考答案:B解析:1.M型超声是图形表示运动结构的波形,提供一组线代表运动界面相对时间的运动状况。2.B型超声是以点显示组织结构的两维图像,点的亮度与回声振幅成正比,图像可用于实时和静态扫描。