哪项是龋病一级预防的内容()
A.根尖周炎应进行恰当治疗
B.早期龋及时充填
C.窝沟封闭、防龋涂料
D.牙列缺失,及时修复
E.不能保留的牙应及时拔除
参考答案:C
—How are you feeling today?
—________ I think I can go to the picnic with you tomorrow.[ ]
A. Not too bad.
B. Much better.
C. Very bad.
D. Not so well.
甲、乙、丙三架直升机同时上升,v甲<v乙<v丙.乙机驾驶员感到自己在下降,这是因为他把参照物选为( )
A.地面
B.甲机
C.乙机
D.丙机