—  What's the model plane look like?

— The wings of the plane are ____of its body. [ ]

A. more than twice the length    

B. twice more than the length

C. more than the length twice    

D. more twice than the length

牙槽骨吸收处的Howship陷窝内的细胞是（）

A.成纤维细胞

B.成牙骨质细胞

C.成骨细胞

D.破骨细胞

E.牙周膜干细胞