鸟类的原沟、享氏结在功能上相当于两栖类的什么结构？
参考答案：胚孔；胚孔的背唇。
同学们，仔细观看这些小动物在哪儿，用in、on或under填空。
1. Aha! It's the apple. It's the book.
2. It's the egg. It's the box (盒子).
3. Aha! It's the tree. Look! It's the tree.
“法律严禁遗弃老人的行为，但难以使人们自觉地孝敬老人。”这句话说明
A．法律的约束力没有道德强
B．法律无法调节婚姻家庭关系
C．法律对部分社会成员还不具有的约束力
D．法治和德治是相辅相成的
Aha! It's the apple. 
It's the book.
It's the egg. 
It's the box (盒子).
Aha! It's the tree. 
Look! It's the tree.