耐火制品取样，在取样单内应记明（），数量，批号及取样日期。
参考答案：砖号
— Was it in April,1970________China succeeded________sending its first satellite into space?
— Yes, that's right . [ ]
A. when; in
B. that; on
C. which; on
D. that; in
二次谐波成像增强超声造影效果的原理是
A．增大微气泡的浓度B．只接收造影剂的二次谐波回声C．谐振时造影剂的散射面积变小D．只接收造影剂的散射面积变小E．二次谐波的回声强度最大时微气泡变小
