To support the enterprise high-availability requirements, which workgroup switch technology can be used to interconnect multiple switches into a single logical unit?

A.
StackWise

B.
EtherChannel

C.
vPC

D.
Flex Links

E.
VSS

Explanation:
Cisco StackWise technology unites up to nine individual Cisco Catalyst 3750 switches into a single logical unit, using special stack interconnect cables and stacking
software. The stack behaves as a single switching unit that is managed by a master switch elected from one of the member switches.
http://www.cisco.com/c/en/us/products/collateral/switches/catalyst-3750-series-switches/prod_white_paper09186a00801b096a.html