The British introduced the Ryotwari system of land revenue collection in:

Malabar region
Travancore
Cochin
All of Kerala

The correct answer is: D) All of Kerala.

The Ryotwari system was a land revenue system introduced by the British in India in the 18th century. Under this system, individual farmers were responsible for paying land revenue directly to the government. This system was introduced in Kerala in 1793, and it remained in place until the 1950s.

The Ryotwari system had a number of advantages over the previous land revenue system, which was based on the collection of revenue from villages. Under the Ryotwari system, the government was able to collect revenue more efficiently, and it was also able to keep a closer eye on the use of land. The system also gave farmers more incentive to improve their land, as they were now responsible for paying the entire revenue themselves.

However, the Ryotwari system also had some disadvantages. One of the main problems was that it was often difficult for the government to collect revenue from farmers who were unable to pay. This led to a number of disputes between the government and farmers. Another problem was that the system was not always fair, as some farmers were able to pay less revenue than others.

Despite its problems, the Ryotwari system was a significant improvement over the previous land revenue system. It helped to improve the efficiency of the government’s revenue collection, and it also gave farmers more incentive to improve their land.

The other options are incorrect because they do not cover the entire state of Kerala. Option A, Malabar region, is incorrect because the Ryotwari system was introduced in all of Kerala, not just the Malabar region. Option B, Travancore, is incorrect because the Ryotwari system was introduced in Travancore, but it was also introduced in other parts of Kerala. Option C, Cochin, is incorrect because the Ryotwari system was introduced in Cochin, but it was also introduced in other parts of Kerala.