Hello can you me posted picture of question

The sample space will be: {1, 2, 3, 4, 5, 6}

Event A is: {Rolling 1,2 or 3}

Complement of event A will contain all those outcomes in the sample space which are not a part of event A.

So, complement of event A will be: {Rolling a 4,5 or 6}

Thus option A gives the correct answer

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