What is the maximum length of any numeric geographic area address in ITU recommendation E.164?

What is the maximum length of any numeric geographic area address in ITU recommendation E.164?
A . 15
B . 18
C . 21
D . 22
E . 25

Answer: A

Explanation:

E.164 defines a general format for international telephone numbers. Plan-conforming numbers are limited to a maximum of 15 digits. The presentation of numbers is usually prefixed with the character + (plus sign), indicating that the number includes the international country calling code (country code), and must typically be prefixed when dialing with the appropriate international call prefix, which is a trunk code to reach an international circuit from within the country of call origination.