We didn't have enough chairs, _____ some of the students had to sit on the floor. [ ]

A. or

B. as

C. so

D. but

胚乳发育的（）方式中，初生胚乳核的第一次分裂将胚囊分隔成两室。

A.核型

B.细胞型

C.沼生目型

D.同时型