Answer:
b) to explore deep spiritual meanings
d) to protect themselves from political or religious persecution
The use of allegory was an important characteristic of literature in Medieval times. Allegory allowed authors to synthesize Biblical and classical traditions in order to explore deep spiritual meanings. It provided a connection between the ancient world and the new "Christian World." Allegory was also a convenient way in which authors could explore this topics in a "veiled" way, in order to protect themselves from political or religious persecution.