Final answer:
The work done by Cyril and Methodius resulted in the development of the Cyrillic alphabet and the translation of religious texts into Slavic languages, aiding in the spread of Christianity.
Step-by-step explanation:
The work done by the monks Cyril and Methodius resulted in the development of the Cyrillic alphabet (option b) and the translation of religious texts into Slavic languages (option c).
Cyril and Methodius, also known as the Apostles to the Slavs, created the Cyrillic alphabet to aid in their missionary efforts to convert the Slavic peoples to Christianity. By translating religious texts into Slavic languages, they made it possible for the Slavs to understand and practice Christianity in their own language.
The spread of Christianity in the Byzantine Empire (option a) and the establishment of monastic schools (option d) were not direct results of the work done by Cyril and Methodius, although their efforts in promoting Christianity did contribute to the overall spread of the religion in Eastern Europe.