腔上囊(法氏囊)随性成熟而萎缩,()月龄左右消失。
A、12
B、10
C、9
D、8
参考答案:A
_____ father is a teacher. [ ]
A. He's
B. His
C. He
D. Him
常用的蜗轮材料为()、()及()等。