食物嵌塞()
A.卡环臂未进入倒凹区
B.基托与黏膜不密合
C.卡环过紧
D.支托凹过深
E.有早接触
参考答案:B
When he was 20 years old, his dream to be a singer _____.[ ]
A. come true
B. achieve
C. hold on to
D. came true
提高料温能改善烧结混合料的透气性是因为()。
A.消除了预热带
B.减少了过湿现象
C.燃烧带变窄