What type of traffic is optimized by GRE tunnels?

The correct answer is that GRE (Generic Routing Encapsulation) tunnels optimize general application traffic. GRE is a tunneling protocol that encapsulates a wide variety of network layer protocols, which allows for the transmission of packets that may not normally be routed across a network.

By using GRE tunnels, organizations can create private, point-to-point links between locations over the public Internet, effectively optimizing the routing of application traffic. This can include various types of application data, such as VoIP, VPN services, or any other IP protocol traffic that needs to be sent securely between two endpoints. The ability to encapsulate this general traffic allows for improved performance and reduces latency, which is essential for optimal application responsiveness.

Regarding the other choices, while static web traffic and heavy video streams may indeed use GRE tunnels, the primary benefit and broad usage of GRE is more aligned with optimizing general application traffic. Inter-cloud traffic could also utilize GRE, but it's a more specific use case compared to the general applicability of GRE tunnels for all sorts of application traffic across different environments.