Refer to Exhibit:The exhibit shows the Connect Peers settings on Amazon Web Services (AWS) transit...

A. The peer GRE address is the FortiGate external interface IP address. This is the IP address of the FortiGate interface that is connected to the transit gateway attachment subnet1. This IP address is used to establish the GRE tunnel between the FortiGate and the transit gateway2. B. The Transit Gateway GRE address is auto-generated. This is the IP address of the transit gateway that is used to establish the GRE tunnel with the FortiGate2. This IP address is automatically assigned by AWS from the Transit Gateway CIDR range that you specify when you create the Connect attachment3.

The other options are incorrect because:

The BGP inside CIDR blocks cannot be any CIDR block with /29. They must be a /29 CIDR block from the 169.254.0.0/16 range for IPv4, or a /125 CIDR block from the fd00::/8 range for IPv64. These are the inside IP addresses that are used for BGP peering over the GRE tunnel4.

The Peer GRE address is not the FortiGate internal interface IP address. The internal interface IP address is used to route traffic from the FortiGate to the VPC subnet where the third-party appliance (such as SD-WAN) is located1. The Peer GRE address is used to route traffic from the FortiGate to the transit gateway over the GRE tunnel2.