A:①②③
B:②③④
C:①③④
D:①②④
计算:16.9÷26
通过对郑氏始孔子鸟化石的研究,推断鸟类可能由古代的哪类动物进化而来( )
Be careful when you come _______ the street, because the traffic is very busy at the moment.