Final answer:
Sino-Japanese and Southeast Asian cultures are similarly influenced by Buddhism, which spread through trade routes and was adapted to local customs, leading to various sects and interpretations. Therefore, the correct option is A.
Step-by-step explanation:
Among the cultural aspects that Sino-Japanese and Southeast Asian cultures share, one of the most notable is the influence of Buddhism. This is evident from the spread of Buddhism across these regions through trade routes, the construction of Buddhist monuments, and the adoption of Buddhist teachings by various segments of society.
For example, Buddhist missionaries traveled from the Indian subcontinent, introducing the religion along the Silk Roads to China and, from there, to Korea, Japan, and Southeast Asia. Buddhism's broader appeal across social strata, particularly due to its opposition to the caste system which was entrenched within Hinduism, allowed it to gain a foothold in these diverse communities.
Over time, it was adapted to incorporate local traditions and culture, giving rise to new sects and interpretations. Thus, the correct answer to the question is 'A. Both are influenced by the principles of Buddhism.'