Which method can be used to address variable-length dial plans?

A.
Overlap sending and receiving.

B.
Add a prefix for all calls that are longer than 10-digits long.

C.
Use nested translation patterns to eliminate inter-digit timeout.

D.
Use the @macro on the route pattern.

E.
Use MGCP gateways, which supportvariable-length dial plans.

Explanation:
Ok, see Dial Plan Solutions, 1-18 and 1-62.
Variable-length numbering plans: Dial string length is determined by timeout. Overlap sending and receiving is enabled, allowing dialed digits to be signaled one by one instead of being sent as one whole number.