The correct option is
D Dissatisfied
The word 'complacent' refers to showing smug or uncritical satisfaction with oneself or one's achievements.
Option A, agitated refers to feeling or appearing troubled or nervous.
Option B, frightened refers to being afraid or anxious.
Option C, degenerate refers to the state of declining or deteriorating physically, mentally and morally.
Option D, dissatisfied refers to not being content or happy with something. Thus, according to the meaning of the given word, 'dissatisfied' will be the correct antonym to 'complacent'.