A. unskilled
B. unsuitable
C. unqualified
D. unable
Appropriate : suitable or proper in the circumstances.
Unskilled : not having or requiring special skill or training.
Unsuitable : not fitting or appropriate.
Unqualified : (of a person) not officially recognized as a practitioner of a particular profession or activity through having satisfied the relevant conditions or requirements.
Unable : lacking the skill, means, or opportunity to do something.
Antonym of Appropriate is Unsuitable
