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CSS is not like other degrees' exams. If someone is not able to clear one or more papers, he again has to appear in all the 12 papers. There is no room for the choice of Repetition or the concept of Marks-Improvement. Secondly, no one ever appears to Improve Marks, everyone here fights for the i) Pass of every paper ii) Score high, and iii) get allocated on the higher marks.

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"But screw your courage to the sticking place,
And we'll not fail." _Shakespeare, 'Macbeth')