副框与板材的侧面可用抽芯铝铆钉紧固，抽芯铝铆钉间距应在300mm左右，紧固时应注意。
参考答案：错
It is ten months since he ______ a doctor.
A．becomes
B．became
C．has become
D．had become
形成垂直食物嵌塞的最常见原因是（）
A.龈 * * 退缩
B.邻牙边缘嵴高度不一致
C.胎面磨损均匀
D.食物溢出沟加深
E.颊、舌面龈退缩
