What is a limitation of IPv6 RA Guard?

What is a limitation of IPv6 RA Guard?
A . It is not supported in hardware when TCAM is programmed
B . It does not offer protection in environments where IPv6 traffic is tunneled.
C . It cannot be configured on a switch port interface in the ingress direction
D . Packets that are dropped by IPv6 RA Guard cannot be spanned

Answer: B

Explanation:

Restrictions for IPv6 RA Guard

Reference: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipv6_fhsec/configuration/xe-16-10/ip6f-xe-16-10-book/ip6-ra-guard.html#GUID-589AF00C-7499-439F-AD23-51005D61CAB7