You have three on-premises networks.
You have an Azure subscription that contains a Basic Azure virtual WAN. The virtual WAN contains a single virtual hub and a virtual network gateway that is limited to a throughput of 1 Gbps.
The on-premises networks connect to the virtual WAN by using Site-to-Site (S2S) VPN connections.
You need to increase the throughput of the virtual WAN to 3 Gbps. The solution must minimize administrative effort.
What should you do?
To increase the throughput of the virtual WAN to 3 Gbps, you need to upgrade the virtual WAN to the Standard SKU. The Basic SKU is limited in features and does not support increasing gateway scale units or higher throughput capabilities. Upgrading to the Standard SKU provides additional features and better performance, which will help in achieving the required throughput with minimal administrative effort.
We want to minimize administrative effort D. Increase the number of scale units https://learn.microsoft.com/en-us/azure/virtual-wan/gateway-settings#s2s
D. Increase the number of gateway scale units: Is incorrect Unsupported for Basic SKU: The Basic SKU does not support increasing gateway scale units to achieve higher throughput. This option is more relevant for Standard or higher SKUs. Because of this I believe the answer is A, we need to upgrade the virtual WAN to Standard SKU first.
https://learn.microsoft.com/en-us/azure/virtual-wan/virtual-wan-faq#what-are-virtual-wan-gateway-scale-units