In this case the answer B is correct; Iron.
Metalworkers in ancient India were renowned for their skills in creating different types of objects that were of very pure quality and the highest standards. These of course were not that common and not just anyone could obtain or afford such items.
Im pretty sure the answer is C because a lot of companies were still downsizing
Byzantium/Constantinople was conquered in 1451, but the empire continued to decline starting around the 18th or 19th centuries. It officially died in WWI. As for how long it was a major threat to Europe, the empire's prime was the 16th century, under Suleiman the Magnificent.
