Which QoS mechanism if any, do you recommend at the headquarters location?

A DMVPN network is being deployed for 10 branch sites to connect to the central headquarters over the Internet. Each branch site connects to the internet via a 1.5 Mb/s ADSL line, and the headquarters connects to the Internet over a 100Mb/s circuit limited to 20 Mb/s by the service provider.

Which QoS mechanism if any, do you recommend at the headquarters location?
A . Rate-limiting the 100 Mb/s circuit to 20 Mb/s
B . Applying hierarchical QoS with parent policy for the overall circuit and child policy for the spokes
C . Traffic shaping the 100 Mb/s circuit to 20 Mb/s
D . QoS is not required in this instance due to maximum traffic being received by the branches being 15 Mb/s

Answer: B