A:保护耳蜗内的听觉感受器
B:防止听觉中枢受损伤
C:保护鼓膜内外气压平衡
D:使咽鼓管张开,保护听小骨
Though he was badly injured, he is now________.
关于平流层的叙述,正确的是( )
—He is ________ and I don't think he'll help us with anything.