Steelmaking is the process of producing steel from iron ore and/or scrap. ... Limiting dissolved gases such as nitrogen and oxygen and entrained impurities (termed "inclusions") in the steel is also important to ensure the quality of the products cast from the liquid steel.
Umayyad Caliphs managed to expand their empire because the Byzantine and Persian empires were weak.
date can help, along with point of view of the author
The answer I would choose is C.