Which statement describes the difference between a manually configured IPv6 in IPv4 tunnel versus an automatic 6to4 tunnel?（）

• A、An automatic 6to4 tunnel does not req uire dual - stack (IPv4 and IPv6) routers at the tunnel endpoints.
• B、An automatic 6to4 tunnel allows multiple IPv4 destinations.
• C、A manually configured IPv6 in IPv4 tunnel allows multiple IPv4 destinations.
• D、A manually configured IPv6 in IPv4 tunnel does not require dual- stack (IPv4 and IPv6) routers at the tunnel endpoints.