A:CH4和C2H4
B:烷烃和环烷烃
C:C3H8和C5H12
D:C2H4和C4H8
The natural ____(景色) of the island is breathtaking.
下列物质,按弹性与塑性分类,与其它物质不同的是( )
一个袋子里有3个黄球,2个红球,1个黑球,请问怎样设计规则才能使双方公平?