A:Oh. I’m afraid I didn’t cook very well.
B:I’m glad you enjoy it.
C:Come again when you are free.
D:It’s not polite of you to say so.
胚胎发育过程中与母体进行物质交换的器官是( )
八年级某位老师在讲授“祖国统一的历史大潮”时,设计了如下板书。其中,方框中的内容应是( )