The guard was given explicit orders about whom to admit.

Solution (By Examveda Team)

Explicit : stated clearly and in detail, leaving no room for confusion or doubt.
Wrong : not correct or true; incorrect.
Inadequate : lacking the quality or quantity required; insufficient for a purpose.
No : not any.
Ambiguous : open to more than one interpretation; not having one obvious meaning.

Antonym of Explicit is Ambiguous