A. to be a marking mechanism that identifies different flows
B. to provide fair queuing for buffered flows
C. to mitigate delays over slow links
D. to limit the bandwidth that a flow can use
Answer: Option D.
The primary reasons you would use traffic shaping are to control access to available bandwidth, to ensure that traffic conforms to the policies established for it, and to regulate the flow of traffic in order to avoid congestion that can occur when the sent traffic exceeds the access speed of its remote, target interface. Reference: Cisco IOS 12.0 Quality of Service, page 94