Fill in the blank: With the User Directory Software Blade, you can create R80 user definitions on a(an) ___________ Server.

A. NT domain

B. SMTP

C. LDAP

D. SecurID

Reference: https://sc1.checkpoint.com/documents/R80/CP_R80_SecMGMT/html_frameset.htm?topic=documents/R80/CP_R80_SecMGMT/126197