下列间接盖髓的适应证中,不正确的是()
A.深龋
B.深龋引起的可复性牙髓炎
C.活髓牙全冠牙体预备后
D.深龋洞,夜间偶有隐痛
E.外伤冠折未露髓
参考答案:D
利用声音在空气中的传播速度,通过计算说明,人要能听见回声,至少离障碍物多远?
I was really anxious about you. You _______ have left home without a word.
A.mustn't
B.shouldn't
C.needn't
D.couldn't