人体的下列结构中,属于器官的是( )
A:
B:
C:
D:
例
uncle
Play tennis
1
aunt
Playing football
2
sister
Playing basketball
3
teacher
Playing ping-pong
4
mother
Playing volleyball
例:My uncle is playing tennis.
①中央集权制度的建立
②造纸术的发明
③文字和度量衡的统一
④张骞出使西域
下图的现象叫____ ,它是由于____ 而形成的.