Blind alley means a course of action that leads nowhere. 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: Blind alley can refer to a course of action that leads nowhere.
• Story example: A writer may use Blind alley when describing a course of action that leads nowhere.
• Exam example: When a sentence contains Blind alley, choose the meaning “a course of action that leads nowhere.”