Dear Barakha,

To avail partial mark the number of choices shaded should not exceed the number of correct choices and must include at least one of the correct choices.
If all four options are shaded for a question for which there are less than four correct answers then the candidate gets zero.

for example if a question has A,C correct option. then

1. if you will answer A,C,D then u will get zero.(exceed the number of correct choice)

2. if you will answer B,D then u will get zero.( does not include any correct choice)

3. if u will answer A,D then you will get partial marking.( include 1 correct choice)

4. if u will answer A then u will get partial marking ( include 1 crrect choice.)

5.  if u will answer A.c then u will get full marks ( include all the correct choice)

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Askiitians Expert 

Amit - IT BHU