Which one of the following is the reason for emitting the negative signal of scowling?

Scowling is a frown with lowered, drawn-together brows and tightened lips. It signals displeasure, and the most direct reading among these options is annoyance: mild irritation at something that is bothering or obstructing you. That is why D is the answer.

• A) Boredom is usually shown by a blank gaze, drooping eyelids, yawning or looking away, not by a scowl.
• B) Impatience shows up as foot-tapping, glancing at the watch, fidgeting or restless movement. A scowl can accompany it, but the question asks for the signal itself, and that points to annoyance.
• C) Disbelief is shown by raised eyebrows, widened eyes, an open mouth or a head tilt. A scowl is the opposite of that open-eyed reaction.

The core concept here is nonverbal communication: facial expressions carry emotional meaning that people read quickly. For Mains GS-IV, this links to emotional intelligence and to reading citizens' non-verbal cues during public dealings, where a scowl can signal that a grievance is being received badly.

Trap: aspirants often pick anger or impatience because scowling looks intense. Anger is stronger and more explosive, while scowling is a milder, controlled display of irritation, so annoyance fits better.