Speaking in a tremulous tone, he took everybody to task.

Answer: Option D

Confident : feeling or showing confidence in oneself or one's abilities or qualities.
Angry : feeling or showing strong annoyance, displeasure, or hostility; full of anger.
Feeble : lacking physical strength, especially as a result of age or illness.
Trembling : shaking or quivering, typically as a result of anxiety, excitement, or frailty.
Tremulous : shaking or quivering slightly.

Synonym of Tremulous is Trembling