How is the aggregator attribute handled with 32-bit AS numbers?

How is the aggregator attribute handled with 32-bit AS numbers?
A . With the same method and attribute as 16-bit AS numbers.
B . With the same method as 16-bit AS numbers, but using the AS4_Aggregator attribute.
C . Aggregation is not yet supported with 32-bit AS numbers.
D . By using a dummy value of 23456 in the 16-bit AS aggregator field. This value lets the router know it needs to read the 32-bit AS number that is contained in the nextTL

Answer: B