Dead set against means strongly opposed to something. This answer is correct because the expression has a fixed figurative meaning in English. In an SSC idiom question, students should match the whole phrase with its accepted meaning rather than translate each word separately.

• Classroom example: Dead set against can refer to a situation involving strongly opposed to something.
• Story example: A writer may use Dead set against when describing a situation involving strongly opposed to something.
• Exam example: When a sentence contains Dead set against, choose the meaning “strongly opposed to something.”