Detailed
A . An expired certificate: An expired SSL/TLS certificate triggers browser warnings about insecure connections. Renewing the certificate will resolve the issue.
References:
CompTIA Cloud+ CV0-003 Study Guide Chapter 6: Secure a Network in a Cloud Environment.

MFA (Multi-Factor Authentication) is a security technique that requires the user to present two or more pieces of evidence to prove their identity when they try to access a system or an application. For example, a password and a physical token, or a fingerprint and a one-time code. MFA can improve the company's security posture by preventing unauthorized access even if the password or single-factor authentication is compromised, as the attacker would also need to have the other factors to log in. According to the web search results, MFA can prevent 99.9% of account attacks1.
SSO (Single Sign-On) is a system that allows the user to use one set of login credentials to access multiple systems and applications that previously may have each required their own logins. SSO can improve productivity and user convenience, but it does not replace MFA. In fact, SSO works in conjunction with MFA, as it can enforce MFA for all the systems and applications that are integrated with SSO2. Therefore, implementing SSO does not mean that MFA is not needed.

The correct answer is D. Reduce the number of NFSv3 mounts to one.
NFSv3 is a network file system protocol that allows clients to access files stored on a remote server. NFSv3 uses TCP or UDP as the transport layer protocol, and typically runs on port 20491.
One of the known issues with NFSv3 mounts is that they can cause performance degradation and unresponsiveness on the client side if there are too many mounts or if there are network connectivity problems. This is because NFSv3 does not handle connection failures or timeouts gracefully, and may keep retrying to access the server indefinitely, blocking other processes or threads. This can result in slow disk speeds, high CPU usage, and system hangs23.
Therefore, one of the possible solutions to this issue is to reduce the number of NFSv3 mounts to one per hypervisor, instead of one per VM. This way, the hypervisor can manage the access to the shared storage appliance more efficiently, and avoid creating too many TCP connections or UDP packets that may overload the network or the server. Reducing the number of NFSv3 mounts can also simplify the configuration and troubleshooting of the network file system.
Increasing caching on the storage appliance may improve the read performance of the NFSv3 mounts, but it will not solve the underlying issue of connection failures or timeouts. Caching may also introduce data inconsistency or corruption issues if the cache is not synchronized with the server.
Configuring jumbo frames on the hypervisors and storage may improve the network throughput and efficiency of the NFSv3 mounts, but it will not solve the underlying issue of connection failures or timeouts. Jumbo frames are larger than standard Ethernet frames, and require that all devices on the network path support them. Jumbo frames may also introduce fragmentation or compatibility issues if they are not configured properly.
Increasing CPU/RAM resources on affected VMs may improve their performance in general, but it will not solve the underlying issue of connection failures or timeouts. Increasing CPU/RAM resources may also be costly and wasteful if they are not needed for other purposes.

The best way to resolve the issue where the autoscaling configuration is creating a new VM every five minutes after deploying a new CI/CD tool to automate new releases of the web application and configuring a script to be executed by the VMs during bootstrapping is to debug the script and redeploy it. Debugging the script means finding and fixing any errors or bugs in the code or logic of the script that may cause unexpected or undesired behavior, such as triggering the autoscaling condition or failing to complete the bootstrapping process. Redeploying the script means updating or replacing the existing script with the corrected or improved version of the script. Reference: [CompTIA Cloud+ Certification Exam Objectives], Domain 4.0 Troubleshooting, Objective 4.5 Given a scenario, troubleshoot automation/orchestration issues.

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.