Kerala has a high density of:

The correct answer is: a) Roads.

Kerala has a high density of roads. The state has a total road length of over 1.2 lakh kilometers, which is more than the national average. The road network in Kerala is well-developed and covers all parts of the state. This has helped to improve connectivity and reduce travel time. The state government has also taken steps to improve the quality of roads in recent years.

The other options are incorrect because:

• Kerala does not have a high density of railways. The state has only one major railway line, which runs from Thiruvananthapuram to Ernakulam.
• Kerala does not have a high density of ports. The state has only two major ports, which are located at Kochi and Kollam.
• Kerala does not have a high density of airports. The state has only three major airports, which are located at Thiruvananthapuram, Kochi, and Kozhikode.