银汞合金充填磨牙合面洞3日有激发痛与自发性隐痛，可能是因为：（）
A．咬合创伤
B．有小穿髓点未发现
C．基底过薄
D．洞较深未加基底
参考答案：B
--Could you tell me ______________ for class this morning?
--I am sorry, Mrs. Lin. I got up so late that i couldn’t catch the first bus.
A．why were you late
B．why you are late
C．why are you late
D．why you were late
蜕皮
