Heart of the matter means the central or most important point. 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: Heart of the matter can refer to the central or most important point.
• Story example: A writer may use Heart of the matter when describing the central or most important point.
• Exam example: When a sentence contains Heart of the matter, choose the meaning “the central or most important point.”