Which statement about UDLD is true?

Which statement about UDLD is true?

A.
The udld reset command resets ports that have been error-disabled by both UDLD and Fast UDLD.

B.
Fast UDLD is configured in aggressive mode.

C.
Only bidirectional link failures can be detected in normal mode.

D.
Each switch in a UDLD topology can send and receive packets to and from its neighbors.