A:金刚石
B:氧气
C:氯化钠晶体
D:铜
我国四大工业基地分布图,图中数字序号代表京津唐工业基地的是( )
用10以内的四个不同自然数组成比例,想想能写几个?
Nobody knew who was the first ________ at school that morning when the window was broken.