Explanation:

- Zabt: This was the revenue system implemented during Akbar's reign. Land revenue was assessed based on crop yields and fixed in cash. It was a standardized system that helped streamline revenue collection.

- Ghari: This was a tax levied during some periods of the Mughal Empire, but it was not the primary revenue system under Akbar.

- Iqta: This was an administrative grant system used earlier in the Delhi Sultanate, not during Akbar's time.

- Charai: This referred to a tax on cattle, but again, not the main revenue system established by Akbar.