颈椎骨折脱位固定用
A．长臂石膏托B．髋“人字形”石膏C．包头石膏背心D．管状石膏E．“8字形”石膏绷带
参考答案：C
---Linda made great progress in her English last term.
--- ____________.
A．So did I
B．So I did
C．So I was
D．So was I
如果声波在耦合介质中的波长为λ，为使透声效果好，耦合层厚度为（）
A.λ/4的奇数倍
B.λ/2整数倍
C.小于λ/4且很薄
D.以上B和C
