Refer to the exhibit. An operations engineer observed a suboptimal routing between R4 and R5. The engineer decided to apply a route leaking on R2 and R3 into 49.2000 area ID. Yet, the traffic flow between R4 and R5 is not via the shortest path R4---R3----R1----R5(metric 24). Which reason for this behavior is true? 

Answer options:

A. IS-IS metric-narrow style is used
B. R2 and R3 are still sending the ATT flag to R1
C. R1 is not part of the IS-IS backbone area
D. IS-IS multipology is not enabled

B