The correct option is B might
The given passage is in past tense as it is a narration of events that have already happened.
The given options are all modal verbs. These are verbs that determine the mood of a sentence, like duty, obligation, possibility, ability, etc.
Options A and C: 'May' and 'might' both refer to possibility. But, they cannot be used in the same context.
Generally, 'may' refers to a present situation and 'might' is the past tense form of 'may', in indirect speech. Also, in the sentence 'might' is already used here: "have happened to Kishan, of what might...", suggesting that 'might' should be used in the previous blank too.
Hence, 'might' is preferred here. So, option A is correct and C is incorrect.
(In practice, 'may' and 'might' are being used interchangeably. But, the distinction between 'may have' and 'might have' still remains.
'May have' is used when the event or situation is 'not known to have occurred'.
'Might have' is used when it is known that 'the event did not occur'.
The latter is preferred here, as the word 'might' is already is use, suggesting that the event has not occurred.)
Option B: 'Can' is not followed by the auxiliary verb 'have'. Hence B is incorrect.
Option D: 'Should' refers to an obligation whereas the sentence refers to a possibility. Also, the modal 'might' is already mentioned, suggesting that 'should' cannot be used as the meanings will contrast.
Hence D is incorrect.