Ambiguous :

Answer: Option D

Auxiliary : providing supplementary or additional help and support.
Responsible : having an obligation to do something, or having control over or care for someone, as part of one's job or role.
Salvageable : rescue (a wrecked or disabled ship or its cargo) from loss at sea.
Clear : easy to perceive, understand, or interpret.
Ambiguous : not easy to perceive, understand, or interpret.

Antonyms of Ambiguous is Clear.