What is the Cisco IOS command to turn on explicit null forwarding by LDP?

A.
ldp explicit-null

B.
mpls forwarding explicit-null

C.
mpls ldp advertise-labels explicit null

D.
mpls ldp explicit-null

Explanation:
When you issue the mpls ldp explicit-null command, Explicit Null is advertised in place of Implicit
Null for directly connected prefixes.
SUMMARY STEPS
1. enable
2. configure terminal
3. mpls ip
4. mpls label protocol {ldp | tdp | both}
5. interface type number
6. mpls ip
7. exit
8. mpls ldp explicit-null [for prefix-acl | to peer-acl | for prefix-acl to peer-acl]
9. exit
10. show mpls forwarding-table [network {mask | length} | labels label [- label] | interface interface |
next-hop address | lsp-tunnel [tunnel-id]] [vrf vpn-name] [detail]
http://www.cisco.com/en/US/docs/ios/12_4t/12_4t2/ftldp41.html