With what feature is the downstream ethernet 1/1/9:1-1/1/9:4 command associated?

With what feature is the downstream ethernet 1/1/9:1-1/1/9:4 command associated?
A . Downlink Failure Detection
B . Uplink Failure Detection
C . Unidirectional Forwarding Detection
D . Bidirectional Forwarding Detection

View Answer

Answer: B