旋转震击式套管整形器的锤体下部有一较宽的环行槽，槽宽略（）旋震式整形器的冲程。
A.大于
B.小于
C.大于等于
D.小于等于
参考答案：A
Be quiet, please. The students _______ a class now. [ ]
A. have
B. had
C. are having
D. were having
远区回声过低，声像图不清楚时，应调节下列哪一项（）
A．增大检测深度
B．使用增益（TGC）补偿调节
C．减小增益
D．换用M型观察
E．调节监视器的显示
