Which three modes are the operating of HDLC? (Choose three)

A.
asynchronous balanced mode (ABM)

B.
normal response mode (NRM)

C.
normal peer mode (NPM)

D.
asynchronous client mode (ACM)

E.
asynchronous response mode (ARM)

Explanation:
Normal response mode allows operation over half-duplex communication links, as
long as the primary is aware that it may not transmit when it has given permission to a secondary.
Asynchronous response mode is an HDLC addition[1] for use over full-duplex links. While
retaining the primary/secondary distinction, it allows the secondary to transmit at any time.
Asynchronous balanced mode added the concept of a combined terminal which can act as both a
primary and a secondary. There are some subtleties about this mode of operation; while many
features of the protocol do not care whether they are in a command or response frame, some do,
and the address field of a received frame must be examined to determine whether it contains a
command (the address received is ours) or a response (the address received is that of the other
terminal).