Q: In this task, you're given a question, along with a context passage. The passage will not have a direct answer to the question, but can include some information and a clue for the answer. Assuming you can only obtain information about one entity in the passage, your job is to determine whether information from the passage can be used to answer the question. Indicate your choice as 'a' for Yes or 'b' for No.
Question: Why did the Nok culture die off about 200 AD on the Jos Plateau? Passage:The Nok culture thrived from approximately 1,500 BC to about 200 AD on the Jos Plateau in north and central Nigeria and produced life-sized terracotta figures that include human heads, human figures, and animals. Iron smelting furnaces at Taruga, a Nok site, date from around 600 BC. The Nok culture is thought to have begun smelting iron by 600-500 BC and possibly some centuries earlier. Kainji Dam excavations revealed iron-working by the 2nd century BC. Evidence of iron smelting has also been excavated at sites in the Nsukka region of southeast Nigeria in what is now Igboland: dating to 2,000 BC at the site of Lejja (Uzomaka 2009) and to 750 BC and at the site of Opi (Holl 2009). The transition from Neolithic times to the Iron Age apparently was achieved indigenously without intermediate bronze production. Others have suggested that the technology moved west from the Nile Valley, although the Iron Age in the Niger River valley and the forest region appears to predate the introduction of metallurgy in the upper savanna by more than 800 years. The earliest iron technology in West Africa has also been found to be contemporary with or predate that of the Nile valley and North Africa, and some archaeologists believe that iron metallurgy was likely developed independently in sub-Saharan West Africa.

A:
b