Explanation
The last incremental backup that was conducted 72 hours ago would be the best option to restore the services to a secure state, as it would contain the most recent data before the ransomware infection. Incremental backups only store the changes made since the last backup, so they are faster and use less storage space than full backups. Restoring from an incremental backup would also minimize the data loss and downtime caused by the ransomware attack. References:
https://www.comptia.org/blog/mature-cybersecurity-response-to-ransomware
https://www.youtube.com/watch?v=HszU4nEAlFc

Benchmarks are predefined sets of configuration standards or best practices for securing information systems and networks. Benchmarks can be used to assess system configurations against the minimum security baseline required by local guidelines or industry regulations. Benchmarks can also provide guidance on how to remediate any deviations or vulnerabilities found during the assessment123 Reference: CompTIA Security+ SY0-601 Certification Study Guide, Chapter 10: Summarizing Risk Management Concepts, page 454; What is a Security Benchmark? - Definition from Techopedia; Security Baselines and Benchmarks - SANS Institute; Security Configuration Benchmarks - CIS

Digital signature is used to verify the integrity of a file/application.

When allowing mobile BYOD devices to access network resources, using a captive portal for user authentication and authenticating users using OAuth are both best practices for authentication and infrastructure security. A captive portal requires users to authenticate before accessing the network and can be used to enforce policies and restrictions. OAuth allows users to authenticate using third-party providers, reducing the risk of password reuse and credential theft. References: CompTIA Security+ Study Guide, pages
217-218, 225-226