简述听觉功能四个发展阶段的内涵和作用。
参考答案：
听觉功能的发展要经过听觉察知、听觉分辨、听觉识别和听觉理解四个连续的阶段。
If your father _ alive, how happy he would be to see youl [ ]
A. is
B. was
C. were
