The correct answer is: A) Ancient maritime trade.
The Periplus of the Erythraean Sea is an anonymous Greco-Roman periplus, or guide to navigation, written in the 1st century CE. It describes the coasts of the Indian Ocean from the Red Sea to the Persian Gulf and the Arabian Sea to Sri Lanka and India. The Periplus is an important source of information about ancient maritime trade, as it provides detailed descriptions of the ports and trade routes of the Indian Ocean region.
The Periplus also provides information about the social structure of Kerala, India, at the time of its writing. It describes the different castes and social groups in Kerala, as well as their customs and traditions. However, the Periplus is not a comprehensive source of information on Kerala, and it should be used with caution.
The Periplus does not provide any information about religious beliefs of the time, and it is not a reliable source of information on early writing systems.