Which three features are benefits of using GRE tunnels in conjunction with IPsec for building site-to-site VPNs？（）

• A、allows dynamic routing over the tunnel
• B、supports multi-protocol （non-IP） traffic over the tunnel
• C、reduces IPsec headers overhead since tunnel mode is used
• D、simplifies the ACL used in the crypto map
• E、uses Virtual Tunnel Interface （VTI） to simplify the IPsec VPN configuration