At one's disposal means available for someone to use. 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: At one's disposal can refer to a situation involving available for someone to use.
• Story example: A writer may use At one's disposal when describing a situation involving available for someone to use.
• Exam example: When a sentence contains At one's disposal, choose the meaning “available for someone to use.”