Which three features are benefits of using GRE tunnels in conjunction with IPsec for building site-to-site VPNs？（）
- Aallows dynamic routing over the tunnel
- Bsupports multi-protocol （non-IP） traffic over the tunnel
- Creduces IPsec headers overhead since tunnel mode is used
- Dsimplifies the ACL used in the crypto map
- Euses Virtual Tunnel Interface （VTI） to simplify the IPsec VPN configuratio