At full stretch means using all one's strength, effort, or resources. 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 full stretch can refer to a situation involving using all one's strength, effort, or resources.
• Story example: A writer may use At full stretch when describing a situation involving using all one's strength, effort, or resources.
• Exam example: When a sentence contains At full stretch, choose the meaning “using all one's strength, effort, or resources.”