Need Help in ISCA..

I have scored 34 in ISCA even after attempting around 90 marks..

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I dont know where the things gone wrong. I referred Study Material only. Should I go for reference book...?

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What should be the exact approach to score more in that subject..?

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In DT also I got 36 and refered T.N Manoharan should I change...?

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Friends Please Help me.