New security vulnerabilities or misconfigurations are introduced is correct.

Changes to an information system or to its runtime environment often introduce unforeseen differences in behavior. Software updates library changes configuration adjustments or new services can create vulnerable combinations or leave insecure defaults in place. That can lead to newly exposed attack surface privilege escalation paths or broken authentication and authorization checks which affect both security and operational stability.

Ongoing maintenance and support expenses decrease is incorrect because making modifications usually requires additional testing monitoring and potential rollback work which tends to increase or at least shift costs rather than reliably decreasing them.

Cloud Monitoring is incorrect because it names a capability rather than describing an effect of system changes. Monitoring may need updating after changes but it is not itself the impact on security and operations.

Overall system efficiency and staff productivity improve is incorrect because changes can either improve or degrade efficiency and productivity. Improvements are possible but they are not guaranteed and so this option is not the best answer for likely impacts on security and operations.

Full AWS Practitioner Certification Question