Final answer:
Azure Firewall provides network traffic filtering across multiple Azure subscriptions and virtual networks, with capabilities for centralized policy enforcement, high availability, and auto-scaling.
Step-by-step explanation:
The service that provides network traffic filtering across multiple Azure subscriptions and virtual networks is a) Azure Firewall. Azure Firewall is a cloud-native, intelligent network firewall service that offers stateful and stateless filtering of network traffic. It is designed to protect Azure Virtual Network resources and can be configured across multiple subscriptions and virtual networks to maintain protection consistency through centralised policy enforcement. This service includes high-availability features and can scale automatically according to the workload traffic.
Other options, such as Azure Load Balancer, Azure VPN Gateway, and Azure Security Center, serve different purposes. The Load Balancer distributes inbound traffic to improve application reliability, the VPN Gateway is used for connections to on-premises networks, and the Security Center provides a unified security management system that strengthens the security posture of your data centers.