Explanation
Infrastructure as code (IaC) is a method of provisioning and managing cloud resources using code or scripts, rather than manual processes or GUI tools. This allows for automation, consistency, scalability, and version control of the infrastructure layer. This would be the best option to deploy a solution to automate new application releases that come from the development team without modifying any configurations in the application code. Reference: CompTIA Cloud+ Certification Exam Objectives, Domain 3.0 Maintenance, Objective 3.4 Given a scenario, implement automation and orchestration to optimize cloud operations.

Explanation
These are the best practices to secure the OS of a new web server that has been provisioned in a cloud environment:
Install TLS certificates on the server: TLS (Transport Layer Security) certificates are digital documents that contain information such as identity, public key, expiration date, etc., that can be used to prove one's identity and establish secure communication over a network. Installing TLS certificates on the web server can encrypt and secure web traffic between the server and the clients, as well as prevent spoofing or impersonation attacks.
Disable password authentication: Password authentication is a method of verifying and authenticating users or devices based on passwords or other credentials. Password authentication can be insecure or vulnerable to attacks such as brute force, dictionary, phishing, etc., especially if passwords are weak, reused, or compromised. Disabling password authentication can enhance security by preventing unauthorized or malicious access to the web server using passwords.
Enable SSH key access only: SSH key access is a method of verifying and authenticating users or devices based on digital keys issued by a trusted authority. SSH key access can provide more security and convenience than password authentication, as it does not require users or devices to remember or enter passwords every time they access the web server. Enabling SSH key access only can ensure that only authorized or trusted users or devices can access the web server using keys.

Explanation
RTO (Recovery Time Objective) is a metric that determines the maximum amount of time that a service can be unavailable or disrupted before it causes unacceptable consequences for the business. RTO is normally measured in minutes, hours, or days, and it is based on the criticality and priority of the service. RTO is one of the key metrics that can determine the service recovery duration, as it defines the target time frame for restoring the service to normal operations after a disaster. For example, if a company has an RTO of four hours for its email service, it means that it aims to recover the email service within four hours after a disaster, such as a server failure or a network outage.

Explanation
Single sign-on (SSO) is a type of authentication mechanism that allows users to access multiple systems or applications with a single login credential. SSO can help users have a seamless experience regardless of the collaboration solution being used, as it can eliminate the need for multiple logins and passwords for different systems or applications. SSO can also improve user convenience, productivity, and security, as it can simplify the login process, reduce login errors, and enhance password management. References: CompTIA Cloud+ Certification Exam Objectives, page 14, section 2.7

Explanation
Identity federation is a type of authentication mechanism that allows users to access multiple systems or applications across different domains or organizations with a single login credential. Identity federation can help integrate the cloud resources of Company A and Company B after Company A has acquired Company B, as it can enable seamless and secure access to both companies' cloud resources using the same IAM solution.
Identity federation can also improve user convenience, productivity, and security, as it can simplify the login process, reduce login errors, and enhance password management. References: CompTIA Cloud+ Certification Exam Objectives, page 14, section 2.7