Keep one's head means stay calm in a difficult 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: Keep one's head can refer to a situation involving stay calm in a difficult situation.
• Story example: A writer may use Keep one's head when describing a situation involving stay calm in a difficult situation.
• Exam example: When a sentence contains Keep one's head, choose the meaning “stay calm in a difficult situation.”