Definition: 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.
Input: Question: What time period did the Byzantine Empire rule? Passage:When Boris I assumed the throne of Bulgaria in 852, the country was still pagan, with the ruling Bulgar elite being Tengriists while the Slavic population practised its own religion. Christianity was already widespread in Bulgaria as the country was established on former territories of the Byzantine Empire, and seems to have been influential. Even one of the sons of Khan Omurtag (r. 814–831), Enravota, converted to Christianity. The Bulgarian nobility was strongly opposed to any form of Byzantine influence in the country and was therefore hostile to Christianity as it was directly associated with the Byzantine Empire. Boris I, however, had many reasons to consider conversion — Bulgaria was situated between two powerful Christian empires, Byzantium and East Francia; Christian doctrine particularly favoured the position of the monarch as God's representative on Earth; and finally, Boris also saw Christianity as a way to overcome the differences between Bulgars and Slavs. The geopolitical situation in the mid 9th century was also favourable because of the increasing friction and rivalry between the Papacy in Rome and the Ecumenical Patriarchate of Constantinople for influence in Central Europe. That struggle between the two churches would give the Bulgarian ruler the opportunity to manoeuvre and negotiate with both, thus extracting favourable concessions while keeping the country out of direct foreign influence. When the Byzantines invaded Bulgaria in the autumn of 863 and demanded conversion to Christianity from Constantinople as the single condition to retreat, Boris I readily accepted and was baptised in the beginning of 864, assuming the Christian name Michael after his spiritual godfather, the Byzantine Emperor Michael III. That step was very unpopular among the nobility, but when they rebelled Boris I dealt decisively with them and executed 52 magnates along with their whole families. When in the following year the Byzantines sturdily demonstrated their determination not to allow the existence of an autocephalous Bulgarian Church, Boris I decided to turn to the Papacy.


b