胎盘小叶的个数约为( )
A.8个B.10个C.18~20个D.22个E.24个
参考答案:C
Visitation time should take into _____ both the needs of the parents and the best interests of the children.[ ]
A. reason
B. statement
C. use
D. account
水域生态系统分为 _______ 生态系统和 __________生态系统,陆地生态系统分为 ________ 、________ 、 _________ 等生态系统。