A fly in the ointment means a small problem that spoils an otherwise good 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 fly in the ointment can refer to a small problem that spoils an otherwise good situation.
• Story example: A writer may use A fly in the ointment when describing a small problem that spoils an otherwise good situation.
• Exam example: When a sentence contains A fly in the ointment, choose the meaning “a small problem that spoils an otherwise good situation.”