which file fulfills client download requests for wanboot and the root file system?

On a WAN Boot server, which file fulfills client download requests for wanboot and the root file
system?

A.
/usr/sbin/wanbootutil

B.
/etc/inet/wanboot.conf

C.
/usr/lib/inet/wanboot/bootlog-cgi

D.
/usr/lib/inet/wanboot/wanboot-cgi