A game changer means something that greatly changes a situation. 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 game changer can refer to a situation involving something that greatly changes a situation.
• Story example: A writer may use A game changer when describing a situation involving something that greatly changes a situation.
• Exam example: When a sentence contains A game changer, choose the meaning “something that greatly changes a situation.”