Answer:
D) 23B+D
Step-by-step explanation:
ISDN stands for Integrated Services Digital Network.
PRI stands for Primary Rate Interface.
ISDN operates on two different service levels:
-Basic Rate Interface (BRI) is used by individuals operating on a small scale.
-Primary Rate Interface(PRI) is used by larger businesses and organizations.
ISDN PRI consists of 23B channels and one 64Kbps D channel represented as 23B+D.