The correct answer is: a) Fixed cash payments.
Land revenue systems in princely states of Manipur were often based on fixed cash payments. This was because the princely states were often under pressure from the British to collect taxes in a way that was easy to administer and monitor. Fixed cash payments were also seen as being more fair than other systems, such as a share of the crop yield, which could be difficult to collect and could lead to disputes.
Option b) is incorrect because a share of the crop yield was not a common system of land revenue in princely states of Manipur. This was because it was difficult to collect and could lead to disputes.
Option c) is incorrect because communal ownership of land was not a common system of land revenue in princely states of Manipur. This was because the princely states were often under pressure from the British to collect taxes in a way that was easy to administer and monitor.
Option d) is incorrect because labor service was not a common system of land revenue in princely states of Manipur. This was because it was seen as being unfair and inefficient.