钢的品种按质量分类可分为普通钢、优质钢和()
A、高碳钢
B、结构钢
C、高优质钢
参考答案:C
下列金属广泛应用于火箭、导弹和飞机制造的是( )
A.铁
B.镁
C.钠
D.铜
The police asked the little boy _____. [ ]
A. where did he live
B. where does he live
C. where he lived
D. where he lives