What is the Name Service Switch (NSS) daemon for resolving names from NT servers?

What is the Name Service Switch (NSS) daemon for resolving names from NT servers?

A.
winbindd

B.
nsswitchd

C.
smbd

D.
nmbd

E.
ldmap

Explanation:
http://www.samba.org/samba/docs/man/manpages-3/winbindd.8.html