超声检验中，脉冲的持续时间叫做：（）
A、脉冲宽度；
B、脉冲振幅；
C、脉冲形状；
D、反射。
参考答案：A
Read and tick or cross.（读音并判断，发音相同的画“√”，不同的画“×”）
1. play sail ( )
2. group proud ( )
3. make pay ( )
4. glove grand ( )
5. wait day ( )
6. say May ( )
--- Don’t you think it necessary that he __________ to Miami but to New York?
--- I agree, but the problem is __________ he has refused to.
A．will not be sent; that
B．not be sent; that
C．should not be sent; what
D．should not send; what
