下面所列楔状缺损的病因中应除去()
A．不正确刷牙方式
B．牙颈部的特殊结构
C．釉质发育不全
D．酸性龈沟液
E．牙体应力疲劳
参考答案：C
Mother wanted to be a good provider, a role she ________ since her marriage to
Father.
A．shoulders
B．shouldered
C．is shouldering
D．has been shouldering
在允许超挖的稳定土层中正常顶进时，管下部（）范围内不得超挖。
A．45°
B．105°
C．135°
D．195°
