胎儿和母体进行物质交换的器官是[ ]
A．脐动脉
B．脐静脉
C．母体血液
D．胎盘
答案：D
简述如何营造一个关心员工、鼓励合作的气氛？
We don''t plan to go to the concert, and so they don''t .
A．so do they
B．they don't too
C．neither don't they
D．they don't either
