A snowball effect means a situation where something grows larger or more serious over time. 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 snowball effect can refer to a situation where something grows larger or more serious over time.
• Story example: A writer may use A snowball effect when describing a situation where something grows larger or more serious over time.
• Exam example: When a sentence contains A snowball effect, choose the meaning “a situation where something grows larger or more serious over time.”