In this English vocabulary question, select the single word that best substitutes the description "eager or quick to argue or fight; aggressively defiant".

Introduction / Context:
The question tests your understanding of precise English vocabulary and one word substitutes. You must identify a word that captures the full idea of being eager or quick to argue or fight and being aggressively defiant. Such a word is often used in descriptions of hostile behaviour, quarrelsome attitudes, or confrontational personalities in literature, newspapers, and psychological descriptions.

Given Data / Assumptions:

• The phrase describes a person who quickly becomes argumentative or violent.
• The behaviour is not just firm, but aggressively defiant.
• The options are "Truculent", "Docile", "Pliable", "Pliant", and "Submissive".

Concept / Approach:
Good vocabulary skills involve recognising subtle differences between words. "Truculent" is the standard word used for someone who is fiercely aggressive, ready to fight, and defiantly hostile. The other words describe people who are gentle, easily controlled, or flexible, which is the opposite of the meaning given in the phrase. Therefore, we must match the idea of aggressive defiance with the correct word from the list.

Step-by-Step Solution:
Step 1: Focus on key ideas in the phrase: eager to argue, ready to fight, and aggressively defiant. Step 2: Recall the meaning of "truculent". It refers to someone who is aggressively defiant, hostile, and likely to argue or fight. Step 3: Consider "docile". This means calm, gentle, and easy to control, which is the exact opposite of aggressive defiance. Step 4: Consider "pliable" and "pliant". Both mean easily bent or easily influenced, again suggesting softness, not aggression. Step 5: "Submissive" refers to someone who easily yields to others, which does not fit the idea of quickness to argue or resist. Step 6: Only "truculent" matches the mood and strength of the description given.

Verification / Alternative check:
You can verify by recalling that "truculent" is often used in phrases like "a truculent attitude" or "a truculent teenager", where the sense is of someone who challenges authority, snaps back, and is hard to manage. None of the other words you would naturally use in such contexts. This cross check confirms that "truculent" is the most accurate one word substitute.

Why Other Options Are Wrong:
"Docile" is wrong because it means quiet and easily managed. "Pliable" and "pliant" both suggest flexibility and readiness to be shaped by others, which is far from aggressive resistance. "Submissive" describes someone who accepts authority and does not resist, which is again opposite to being defiant. Thus all these options contradict the aggressive tone of the phrase.

Common Pitfalls:
Many students confuse difficult words simply based on their sound or because they have seen them only once or twice. Another mistake is not paying enough attention to the emotional tone of the phrase, such as aggressiveness or defiance. Building strong vocabulary requires reading extensively, learning words in context, and repeatedly revising them with examples. This will reduce confusion between near synonyms and antonyms in exams.

Final Answer:
The correct one word substitute is Truculent.