At a premium means scarce and therefore valuable. 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: At a premium can refer to a situation involving scarce and therefore valuable.
• Story example: A writer may use At a premium when describing a situation involving scarce and therefore valuable.
• Exam example: When a sentence contains At a premium, choose the meaning “scarce and therefore valuable.”