牙齿萌出特点不包括（）

A.左右对称萌出

B.下牙先于上牙萌出

C.女孩比男孩换牙早

D.乳牙换牙时可有"生理性流涎"现象

E.乳恒牙换牙时间比顺序重要

-That actor often joins in different activities in Beijing. Do you know __________?

-For 5 years.[ ]

A. how soon he will come back

B. how long he has stayed there

C. when he went there

D. how long has he been there