Assuming Three Routers (A, B, and C) Uses BGP as the Routing

Assuming three routers (A, B, and C) uses BGP as the routing protocol. A sends Update packets to B and B sends the Update packets to C. Which of the following attributes meet the following two conditions? (1) A can select whether to carry this attribute in Update packets. (2) If B receives an Update packet carrying this attribute, B still advertises the Update packet to C although B cannot identify this attribute. Then, Router C may identify and use this attribute.

A) Multi_Exit_Disc
B) Local_Pref
C) Community
D) Aggregator