为什么使用75%硅铁作热法炼镁的还原剂?
参考答案:
含硅量超过75%以后,镁产出率高;含硅量越高的硅铁其价格越贵;综合还原效率和经济因素,选用75%硅铁。
---Could you please tell us _____ the famous singer will come for his performance?
---Probably in weeks, and the tickets won’t be expensive.
A.how often
B.how long
C.how soon
D.how much
颈浅淋巴结常常因为哪一部位的病变扩散而累及()
A.牙槽嵴或扁桃体
B.舌前2/3
C.咽
D.喉
E.鼻咽部