Which feature in Cisco WebEx is the most important differentiator compared to other vendors in the collaboration technology?

Which feature in Cisco WebEx is the most important differentiator compared to other vendors in the collaboration technology?

A.
Cisco WebEx is always installed on-premises

B.
Cisco WebEx could be installed or collocated with Cisco Unified Communications Manager.

C.
With an account, everyone can join Cisco WebEx meetings.

D.
Web conferencing service is delivered over a proprietary network, which is optimized for security, performace, and reliability.