A long face means a sad or disappointed expression. 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 long face can refer to a sad or disappointed expression.
• Story example: A writer may use A long face when describing a sad or disappointed expression.
• Exam example: When a sentence contains A long face, choose the meaning “a sad or disappointed expression.”