钢材的化学成分，对钢材的（）和金属组织等方面有着决定性影响。
参考答案：机械性能
_____ was most shocking about the tornadoes in America was that they threatened six states
and killed more than 100 persons. [ ]
A. That
B. Which
C. Why
D. What
陆相沉积的岩石以（）和（）为主。
