Correct Answer:
C. Heroism
The correct answer is Heroism. Valour is defined as great courage, especially in battle, or bravery. Heroism perfectly captures this meaning, referring to the quality of being a hero or showing immense courage and noble qualities. For instance, a soldier displaying valour on the battlefield is performing an act of heroism. Option A, Stable, means firm or steady, which is unrelated to courage. Option B, Coward, is an antonym, representing a lack of courage. Option D, Fear, is an emotion often overcome by valour, making it the opposite of the quality in question. Therefore, heroism is the most accurate synonym, directly reflecting the essence of bravery and courageous acts.