Larry asks Bill and Peter to go on a picnic with him, but        of them wants to, because they have work to do.

A．either

B．any

C．neither

D．none

下列关于超声造影的概念错误的是（）。

A.微气泡大小与回声信号强度有关

B.超声波发射功率越大微气泡回声越强

C.深度越大微气泡回声越强

D.微气泡浓度越小微气泡回声越弱

E.微气泡弥散度越大微气泡回声越易减弱