Mughal Zagir refers to the practice of granting a revenue right or land revenue assignment to a Mughal officer by the Emperor. Option 1, providing rent-free land, is not an accurate explanation of Mughal Zagir. Option 2, zamindar`s property, is also incorrect as Mughal Zagir does not involve the granting of property to zamindars. Option 3, giving an officer the right to revenue, is the correct explanation as it reflects the essence of Mughal Zagir. The Emperor would assign a specific area or revenue collection responsibility to an officer, who would then collect the revenue from that assigned area. Option 4, giving cash salary to Man-sabdar, is not a correct explanation of Mughal Zagir. Hence, the correct answer is option 3.