In principle means in general idea, though not always in detail. 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: In principle can refer to a situation involving in general idea, though not always in detail.
• Story example: A writer may use In principle when describing a situation involving in general idea, though not always in detail.
• Exam example: When a sentence contains In principle, choose the meaning “in general idea, though not always in detail.”