You are designing a strategy to allow internal users in Dallas to resolve domain names. What are three possible ways to achieve the goal？（）
- A Configure the internal DNS server to have a root zone.
- B Configure the Dallas DNS server to use the default root hints.
- C Configure the Dallas DNS server to forward all request for the external namespace to the external DNS server.
- D Create a caching-only DNS server on the perimeter network.
- E Create a stub zone for the external namespace on the Dallas DNS server.