Answer : 2. "The northern part of India was ruled over by Razia Sultana."
Explanation :

In Active Voice, a sentence emphasizes the subject, performing an action.
In Passive Voice, a sentence emphasizes the action or the object of the sentence.
The given sentence is in the active voice and 'Razia Sultana' is the subject and 'the northern part of India' is the object.
When we convert this sentence into passive voice, the subject 'Razia Sultana' of the active voice becomes the object, the object 'the northern part of India' becomes the subject.
The passive format "was + V3 (ruled)" should be used.
This is the active and passive voice rule for the past simple tense.
Hence, the correct sentence is 'The northern part of India was ruled over by Razia Sultana'