Which interface-level command is needed to turn on 802.1X authentication? 

Answer options:

A. dot1x system-auth-control
B. dot1x pae authenticator
C. aaa server radius dynamic-author
D. authentication host-mode single-host

B

Reference: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/12-2/31sg/configuration/guide/conf/dot1x.html