在一个苹果中生有7个发育成熟的种子,在它完成受精过程时,最少需要的精子数是( )
A.7个
B.14个
C.21个
D.28个
答案:B
__________ like to play chess.[ ]
A. My father and I
B. I and My father
C. My father and me
D. Me and my father
我国的工业部门可分为____________和____________两大类。