The correct answer is: b) Arab traders.
The term “Malabar” was first used by Arab traders to denote the coastal region of Kerala. The Arabs were the first to trade with Kerala, and they used the term “Malabar” to refer to the region where they conducted their trade. The term “Malabar” is derived from the Arabic word “Malabar”, which means “land of pepper”. Pepper was one of the main commodities that the Arabs traded with Kerala, and the term “Malabar” came to be used to refer to the entire coastal region of Kerala.
The other options are incorrect. The Chinese travelers did not use the term “Malabar” to denote the coastal region of Kerala. The Portuguese explorers were the first Europeans to reach Kerala, and they used the term “Malabar” to refer to the region where they landed. The British colonizers also used the term “Malabar” to refer to the region, but they did not coin the term.