小儿出生后正常情况下造血器官主要是（）。

A.卵黄囊

B.中胚叶

C.肝

D.骨髓

E.脾

—What do we need to buy?    

—We need _____.[ ]

A. two carton of milk  

B. two cartons of milks  

C. two cartons of milk  

D. two carton of milks