What will happen if an update is received with an unrecognized optional non-transitive attribute?

What will happen if an update is received with an unrecognized optional non-transitive attribute?
A . The router will accept the update and send a notification.
B . The router will not accept the update and send a notification.
C . The router will accept the update and ignore the attribute.
D . The router will accept the update and propagate the attribute.

Answer: C