Démentir belong to the 3
rd group. Démentir is a common french verb.
Démentir is conjugated the same way that verbs that end in :
-tir
Démentir is conjugated with
auxiliary avoir.
Démentir verb is
direct transitive.
French verb démentir can be conjugated in the reflexive form:
Se démentir
Démentir verb is a direct transitive verb, so passive voice can be used.