Answer:
Indian trade
Explanation:
We don´t have a categoric knowledge about the origins of Islam in Indonesia, but according to historical evidence available, it seems that trade played a major role in the arrival of Islam in Indonesia in the 13th century. Two Muslim trading kingdoms existed in northern Sumatra, Samudra-Pasai and Perlak by then. At Samudra-Pasai, there´s a royal tomb completely inscribed in Arabic dated 1297. Further developments in the region also point at an expansion of trade with India and in the Indian Ocean as a major factor in the spreading of Islam in Indonesia.
I would say B monotheism and C writing system not yet deciphered
hope this helps
Exceptionally high population densities occur in the Yangtze delta, the Pearl River Delta, and on the Chengdu Plain of the western Sichuan Basin. Most of the high-density areas are coterminous with the alluvial plains on which intensive agriculture is centred.
