Have a field day means enjoy a chance to do something freely or successfully. 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: Have a field day can refer to a situation involving enjoy a chance to do something freely or successfully.
• Story example: A writer may use Have a field day when describing a situation involving enjoy a chance to do something freely or successfully.
• Exam example: When a sentence contains Have a field day, choose the meaning “enjoy a chance to do something freely or successfully.”