Heaven knows means nobody knows; it is uncertain. 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: Heaven knows can refer to a situation involving nobody knows; it is uncertain.
• Story example: A writer may use Heaven knows when describing a situation involving nobody knows; it is uncertain.
• Exam example: When a sentence contains Heaven knows, choose the meaning “nobody knows; it is uncertain.”