Comprehensive and Detailed In-Depth Step-by-Step Explanation:Palo Alto Networks offers a range of firewall solutions designed to secure various environments, including public cloud deployments. The Systems Engineer Professional - Software Firewall documentation specifies the following firewalls as suitable for public cloud environments:

CN-Series firewall (Option A): The CN-Series firewall is specifically designed for containerized environments and is deployable in public cloud environments like AWS, Azure, and Google Cloud Platform (GCP). It integrates with Kubernetes to secure container workloads in the cloud.

Cloud NGFW (Option C): Cloud NGFW is a cloud-native firewall service tailored for public cloud environments such as AWS and Azure. It provides advanced security features like application visibility, threat prevention, and scalability without requiring traditional hardware or virtual machine management.

VM-Series firewall (Option D): The VM-Series firewall is a virtualized next-generation firewall that can be deployed in public cloud environments (e.g., AWS, Azure, GCP) to protect workloads, applications, and data. It offers flexibility and scalability for virtualized and cloud-based infrastructures.

Options B (PA-Series firewall) and E (Cloud ION Blade firewall) are incorrect. The PA-Series firewalls are physical appliances designed for on-premises data centers and do not natively protect public cloud environments. The Cloud ION Blade firewall is not a recognized Palo Alto Networks product in this context, as it is not part of the software firewall portfolio for public clouds.

References: Palo Alto Networks Systems Engineer Professional - Software Firewall, Section: Public Cloud Security Solutions, VM-Series Deployment Guide, CN-Series Deployment Guide, and Cloud NGFW Documentation.