I know that the answer to the question "What was the cause of the Buddhist religion's influence from other cultures?" is in "The gradual spread of Buddhism into adjacent areas meant that it came into contact with new ethnical groups. During this period Buddhism was exposed to a variety of influences, from Persian and Greek civilization, to changing trends in non-Buddhist Indian religions—themselves influenced by Buddhism. Striking examples of this syncretistic development can be seen in the emergence of Greek-speaking Buddhist monarchs in the Indo-Greek Kingdom, and in the development of the Greco-Buddhist art of Gandhāra. A Greek king, Menander, has even been immortalized in the Buddhist canon.". Can you tell me what it is?
The answer to this question is:
The gradual spread of Buddhism into adjacent areas