What is the marking scheme and negative marking pattern in UPSC Prelims?

In the UPSC Preliminary Examination, both papers follow a strict negative marking pattern where one-third (1/3rd) of the marks assigned to a question are deducted for every incorrect response. 
The marking details for the two papers are as follows:

General Studies Paper I (Merit Paper):

• Total Questions: 100
• Marks per Correct Answer: +2 marks
• Negative Marks per Wrong Answer: -0.66 marks (1/3rd of 2 marks)
  

GS Paper II (CSAT - Qualifying Paper):

• Total Questions: 80
• Marks per Correct Answer: +2.5 marks
• Negative Marks per Wrong Answer: -0.83 marks (1/3rd of 2.5 marks) 

Critical Marking Rules

• Multiple Answers: If you mark more than one option for a single question, it is treated as a wrong answer, even if one of your choices is correct. The standard 1/3rd penalty will be applied.
• Unattempted Questions: There is no penalty for questions left blank. No marks are awarded or deducted.
• Qualifying Nature: While Paper II has higher negative marks per question, it is only qualifying; you must secure at least 33% (66 marks) for your Paper I to be evaluated for merit.