In the Cisco Resilient Ethernet Protocol (REP), how many ports are always blocking?

A.
zero

B.
at least one

C.
at least two

D.
at least four

E.
at least three

Explanation:
http://www.cisco.com/en/US/prod/collateral/switches/ps6568/ps6580/prod_white_paper0900aecd8
06ec6fa.pdf
Cisco REP Operation
With REP at least one port is always blocked in any given segment, that is, the alternate port.