Final answer:
BH Streeter's hypothesis discusses the relationships between the Synoptic Gospels, suggesting that gospel writers utilized different Mystery traditions to shape the narrative of Jesus.
Step-by-step explanation:
BH Streeter's hypothesis concerning the probable relationships between the Synoptic Gospels posited that the authors of the Gospels derived their material from different Mystery traditions. This theory suggests that the spiritual experiences once had in the Mystery schools of various cultures were transformed, culminating in the narrative of the historical Jesus as told through the Gospels. The material used by the authors such as Matthew, Mark, Luke, and John, emerged from these separate traditions, though the specific methods of incorporation remain unclear according to Streeter.