This is because the Linux1 EC2 instance is not accessible directly from the internet using its public IP address in AWS.
An internet gateway is a horizontally scaled, redundant, and highly available VPC component that allows communication between instances in your VPC and the internet. Without an internet gateway, the Linux1 EC2 instance cannot receive or send traffic to or from the internet, even if it has a public IP address assigned to it.
To fix this issue, you need to attach an internet gateway to the Spoke VPC A and configure a route table that directs internet-bound traffic to the internet gateway. You also need to ensure that the Linux1 EC2 instance has a security group that allows inbound and outbound traffic on the desired ports.

B: The default network ACL is configured to allow all traffic. This means that when you create a VPC, AWS automatically creates a default network ACL for that VPC, and associates it with all the subnets in the VPC1. By default, the default network ACL allows all inbound and outbound IPv4 traffic and, if applicable, IPv6 traffic1. You can modify the default network ACL, but you cannot delete it1. C. Network ACLs are stateless, and inbound and outbound rules are used for traffic filtering. This means that network ACLs do not keep track of the traffic that they allow or deny, and they evaluate each packet separately1. Therefore, you need to create both inbound and outbound rules for each type of traffic that you want to allow or deny1. For example, if you want to allow SSH traffic from a specific IP address to your subnet, you need to create an inbound rule to allow TCP port 22 from that IP address, and an outbound rule to allow TCP port 1024-65535 (the ephemeral ports) to that IP address2.
The other options are incorrect because:
* You can use network ACL and security group at the same time. Network ACL and security group are two different types of security layers for your VPC that can work together to control traffic3. Network ACLacts as a firewall for your subnets, while security group acts as a firewall for your instances3. You can use both of them to create a more granular and effective security policy for your VPC.
* Network ACLs are not tied to an instance. Network ACLs are associated with subnets, not instances1. This means that network ACLs apply to all the instances in the subnets that they are associated with1. You cannot associate a network ACL with a specific instance. However, you can associate a security group with a specific instance or multiple instances3.

To deploy a FortiGate HA solution in AWS using Terraform, you need to create an AWS IAM user with permissions to access the AWS resources and services required by the FortiGate-VM. You also need to use CloudShell to install Terraform, which is a tool for building, changing, and versioning infrastructure as code.

For administrators seeking to gain insights into user activities and data within major SaaS applications across multicloud environments, deploying FortiCASB (Cloud Access Security Broker) is the most effective solution (Option C).
Role of FortiCASB: FortiCASB is specifically designed to provide security visibility, compliance, data security, and threat protection for cloud-based services. It acts as a mediator between users and cloud service providers, offering deep visibility into the operations and data handled by SaaS applications.
Capabilities of FortiCASB: This product enables administrators to monitor and control the access and usage of SaaS applications. It helps in assessing security configurations, tracking user activities, and evaluating data movement across the cloud services. By doing so, it assists organizations in enforcing security policies, detecting anomalous behaviors, and ensuring compliance with regulatory standards.
Integration and Functionality: FortiCASB integrates seamlessly with major SaaS platforms, providing a centralized management interface that allows for comprehensive analysis and real- time protection measures. This integration ensures that organizations can maintain control over their data across various cloud services, enhancing the overall security posture in a multicloud environment.

AWS NAT gateway allows instances in a private subnet to connect to the internet or other AWS services without using NAT instance. the main routing table sends internet traffic from the private subnet instances to the NAT gateway, then NAT gateway sends traffic to the IGW using the source IP address of the elastic IP address.
Deploy a NAT gateway with an EIP in the public subnet, edit route tables, select Private-route and add a new route destination 0.0.0.0/0 to target the NAT gateway.