A:可能是5
B:一定是5
C:可能是9
D:一定是9
人和动物同住一个地球村,两者的根本区别是( )
化学就在我们身边,下列叙述不是化学变化的是( )
You'd better not ask him about the problem. He's new here and he knows ______ about it.