Familiar ground means a subject or situation one knows well. 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: Familiar ground can refer to a subject or situation one knows well.
• Story example: A writer may use Familiar ground when describing a subject or situation one knows well.
• Exam example: When a sentence contains Familiar ground, choose the meaning “a subject or situation one knows well.”