Router R1, a branch router, connects to the Internet using DSL. Some traffic flows through a GRE and IPsec tunnel, over the DSL connection, and into the core of an Enterprise network. The branch also allows local hosts to communicate directly with public sites in th e Internet over this same DSL connection. Which of the following answers defines how the branch NAT config avoids performing NAT for the Enterprise directed traffic but does perform NAT for the Internet - directed traffic?（）

A. By not enabling NAT on the I Psec tunnel interface
By not enabling NAT on the GRE tunnel interface
C. By configuring the NAT - referenced ACL to not permit the Enterprise traffic
D. By asking the ISP to perform NAT in the cloud