Which statement about the application of QoS in a voice-enabled network is true?

Which statement about the application of QoS in a voice-enabled network is true?

A.
QoS mechanisms are typically used to increase available bandwidth.

B.
QoS mechanisms should be able to provide acceptable voice quality in congested networks.

C.
Fragmentation is used to create smaller voice packets to allow them to be transported more easily.

D.
RSVP is only applicable in a network that does not experience congestion.