Assouplir belong to the 2nd
group. Assouplir is a common french verb.
Assouplir is conjugated the same way that verbs that end in : -ir
Assouplir is conjugated with auxiliary avoir
Assouplir verb is
French verb assouplir can be conjugated in the reflexive form: S'assouplir
verb is a direct transitive verb, so passive voice can be used.