A house of cards means a weak plan or system that can easily fail. 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: A house of cards can refer to a weak plan or system that can easily fail.
• Story example: A writer may use A house of cards when describing a weak plan or system that can easily fail.
• Exam example: When a sentence contains A house of cards, choose the meaning “a weak plan or system that can easily fail.”