Which of the following best describes the implementation challenges that are associated with variable-length numbering plans?

A.
the variable number of extensions that need to be implemented

B.
the number of trunks that need to be assigned

C.
the mapping between IP addresses and extension numbers

D.
the identification of the number of digits that need to be dialed before the call is routed

E.
the degree in which the dial plan varies

Explanation: