What does the global command “udld enable” accomplish?

A.
Enables all fiber-optic LAN ports for Unidirectioinal Link Detection (UDLD)

B.
Enables all copper media LAN ports for Unidirectioinal Link Detection (UDLD)

C.
Overrides the default UDLS setting for all ports

D.
Globally enables all ports on the device for Unidirectional Link Detection (UDLS)

Explanation:

Enabling UDLD Globally
Beginning in privileged EXEC mode, follow these steps to enable UDLD globally on all fiber-optic interfaces on the switch:

To disable UDLD globally on fiber-optic interfaces, use the no udld enable global configuration command.
Reference:
http://www.cisco.com/en/US/docs/switches/lan/catalyst3550/software/release/12.1_4_ea1/configuration/guide/swudld.html