Explanation
You should lock your computer by pressing Windows+L or CTRL-ALT-DELETE and then click "Lock Computer", because this is the most effective way to protect sensitive data in your computer when you go out for lunch. By locking your computer, you are preventing unauthorized access to your computer and its contents, as well as complying with the organization's access control policy and information security policy.
Locking your computer requires a password or a biometric authentication to unlock it, which adds a layer of security to your data. The other options are not sufficient or reliable, as they do not prevent someone from accessing your computer or viewing your screen. References: [CQI & IRCA Certified ISO/IEC 27001:2022 Lead Auditor Training Course], ISO/IEC 27001:2022 Information technology - Security techniques - Information security management systems - Requirements, How to lock your PC