This sentence improvement item tests your choice of the most appropriate word to describe union violence in the sentence "Twelve workers were killed in the conflict between two trade unions".

Introduction / Context:
This question asks you to select the most suitable word to replace conflict in a sentence about trade unions where twelve workers were killed. The sentence Twelve workers were killed in the conflict between two trade unions suggests that the situation was violent and physical rather than just a simple disagreement. In such a context, clash is a more appropriate word, because it commonly refers to violent fights or serious confrontations between groups. Your job is to choose the word that best matches the severity and nature of the incident described.

Given Data / Assumptions:
From the sentence, we can extract the following details.

• Number of casualties: Twelve workers were killed, indicating a serious and violent event.
• Groups involved: two trade unions, which implies organised groups of workers.
• Original word: conflict, a general word that can refer to disagreements at many levels.
• Context: the event led to deaths, so it was not merely verbal or minor.
• The replacement should capture the sense of a violent encounter between opposing sides.

Concept / Approach:
Words like conflict, quarrel, clash, confrontation, and argument all describe forms of disagreement, but they differ in strength and typical usage. Quarrel and argument usually describe verbal disputes, often between individuals, and do not necessarily imply physical violence. Confrontation suggests a face to face meeting that may or may not lead to violence. Clash, on the other hand, is frequently used in news reports to describe violent encounters between groups such as protesters, police, or unions, often resulting in injuries or deaths. Therefore, in a sentence where workers were killed, clash is the most precise and natural choice.

Step-by-Step Solution:

Verification / Alternative check:
Read the improved sentence: Twelve workers were killed in the clash between two trade unions. This sounds like a typical news headline or report and clearly suggests that the unions engaged in a violent fight. If we replace clash with quarrel or argument, the sentence becomes illogical, because people are not normally killed in a simple argument. Confrontation comes close, but it is broader and less vivid; it does not immediately convey the idea of a violent fight leading to deaths. This supports clash as the strongest and most accurate word here.

Why Other Options Are Wrong:
Option A, quarrel, usually describes a small dispute, often verbal, and is far too weak for an incident involving multiple deaths. Option C, confrontation, can describe a serious face to face encounter, but it does not necessarily imply casualties; it is therefore less precise given the information about twelve workers being killed. Option D, No improvement, would keep conflict, which is a general term and does not convey the idea of violent fighting as powerfully as clash does. Option E, argument, is again too mild and most commonly refers to verbal disagreement. Thus, clash is the best fit.

Common Pitfalls:
Many learners treat conflict, quarrel, confrontation, and clash as near synonyms without noticing the differences in intensity and typical usage. In exam questions, small nuances in meaning often determine the correct choice. To improve your performance, pay attention to how these words are used in newspapers and serious articles. For example, headlines often say police and protesters clashed or union clashes turned violent. Recognising these patterns will help you choose more precise words when required. Always connect the vocabulary choice with the broader context, such as whether there was violence or only disagreement.

Final Answer:
The improved sentence should be: Twelve workers were killed in the clash between two trade unions.