Common ground means shared opinions or interests. 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: Common ground can refer to a situation involving shared opinions or interests.
• Story example: A writer may use Common ground when describing a situation involving shared opinions or interests.
• Exam example: When a sentence contains Common ground, choose the meaning “shared opinions or interests.”