Regarding the British land revenue settlements in India, consider the following statements:

I. The Permanent Settlement of Bengal fixed the revenue demand permanently with zamindars.
II. Under the Ryotwari system, the government directly collected revenue from the peasants.
III. The Mahalwari system was prevalent in large parts of northern and central India.
IV. All three systems (Permanent, Ryotwari, Mahalwari) were equally successful in protecting the rights of the cultivators.
Which of the above statements are correct?