In the Cisco Catalyst 6500-E Series chassis, what are three key chassis specifications? (Choose three.)
A. requires Cisco IOS 12.2(1) SXD and beyond
B. three-slot chassis supports CEF720 line cards
C. is backward-compatible with all existing software versions
D. six- and nine-slot chassis support only 6000-W power supplies
E. supports all existing supervisors, line cards, switch fabrics, and software releases
