Which two statements about GRE tunnels are true? (Choose two.)
A. GRE encapsulates the original packet
B. GRE tunnels operate in GRE/IP mode by default
C. The IP header encapsulates the GRE header
D. The carrier protocol adds the delivery header
E. GRE tunnels operate in GRE/IPsec mode by default
A B is correct in my opinion.
D is wrong because GRE is a carrier, so GRE encapsulates the original packet (answer A). D looks ok, but A fits better.
carrier protocol = GRE (https://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/WAN_and_MAN/P2P_GRE_IPSec/P2P_GRE/2_p2pGRE_Phase2.html).
Why D is wrong?