The correct answer is: d) Rubber.
Rubber is the most important commercial crop in Kerala. It is grown in the highland areas of the state. The main rubber-producing districts are Idukki, Kottayam, Ernakulam, and Thrissur.
Banana is the second most important commercial crop in Kerala. It is grown in the lowland areas of the state. The main banana-producing districts are Palakkad, Malappuram, and Kozhikode.
Coconut is the third most important commercial crop in Kerala. It is grown in both the lowland and highland areas of the state. The main coconut-producing districts are Kollam, Alappuzha, and Pathanamthitta.
Cashew is the fourth most important commercial crop in Kerala. It is grown in the lowland areas of the state. The main cashew-producing districts are Kannur, Kasaragod, and Wayanad.
The following are some of the reasons why rubber is the most important commercial crop in Kerala:
- Rubber is a major export earner for Kerala.
- Rubber provides employment to a large number of people in Kerala.
- Rubber is a major source of raw material for the manufacturing industry in Kerala.
- Rubber is a major source of income for the farmers in Kerala.