The suggested answer is A.
A VSS is network system virtualization technology that pools multiple Cisco Catalyst 6500 Series Switches into one virtual switch, increasing operational efficiency, boosting nonstop communications, and scaling system bandwidth capacity to 1.4 Tbps.
Reference:http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps9336/prod_qas0900aec d806ed74b.html