‘Pull your socks up’ means:

The correct option is D. To improve. The idiom 'pull your socks up' means to make a greater effort to improve your work or behavior because it is not good enough. It implies a need to perform better or to work harder.

• A. To finish: This idiom does not mean to complete a task.
• B. To get ready: While it involves preparation, the core meaning is about improving performance, not just getting prepared.
• C. To start: This idiom is not about initiating an action but rather about enhancing an ongoing effort or performance.