下列现象不属于扩散的是( )
A:炒菜时香飘满屋
B:长期堆煤的墙内部变黑
C:踏水过河时水变浑
D:水中加糖,整杯水变甜
Yesterday my father ___________ his friends ___________ Tian'anmen Square (天安门广场).