氟化物防龋作用机制是()
A.降低釉质表层的溶解度
B.改变口腔生态环境,不利于细菌生长
C.抑制糖蛋白在釉质表面的黏附
D.促进釉质再矿化
E.以上均正确
参考答案:E
— How do you find ____ dress in the shop window?
— Oh, it's beautiful. She will be pleased if she can have it as ____ birthday present. [ ]
A. a; a
B. a; the
C. the; a
D. the; the
I can’t _____ his failure.It is unbelievable.
A.seek for
B.bring up
C.get away with
D.account for