In the following question, out of the four alternatives, select the alternative which is the best one-word substitute for the phrase: A system that favours progress and gradual improvement through reforms.

Introduction / Context:
This vocabulary question asks for a one word substitute that summarises a descriptive phrase. The phrase describes a system that favours progress and gradual improvement through reforms. Many political and social systems can be either conservative, resisting change, or reformist, supporting change through lawful and gradual means. Recognising the correct abstract noun that names such a belief or system is essential here.

Given Data / Assumptions:
- The phrase to be replaced is: A system that favours progress and gradual improvement through reforms. - Options are Violation, Impairing, Preservation and Reformism. - The system described values change in a constructive and lawful manner. - We are expected to know common political and social terms.

Concept / Approach:
The word reforms refers to changes made to improve a system, and a doctrine or movement that supports governing by such reforms is called reformism. Reformism is the belief in gradual change rather than sudden revolution. The other options do not match this idea. Violation relates to breaking rules or laws, impairing means damaging and preservation is about keeping things unchanged. None of these expresses favouring progress through reform.

Step-by-Step Solution:
Step 1: Focus on the key elements in the phrase: favours progress, gradual improvement and through reforms. Step 2: Recall that ism often signifies a doctrine, belief or system, such as socialism, capitalism and nationalism. Step 3: Recognise reformism as the doctrine or practice of supporting reforms to achieve progress. Step 4: Compare with other options: Violation means breaking a rule, which is negative; Impairing suggests harming something; Preservation emphasises keeping the existing state. Step 5: Conclude that only Reformism aligns with support for progress through structured reforms.

Verification / Alternative check:
In political science and history, reformism is used to describe movements that seek change within existing legal and institutional frameworks, for example, reformist wings of political parties that push for welfare policies or administrative improvements. This exactly reflects favouring progress and gradual improvement through reforms. By contrast, a preservationist approach would resist change and aim to conserve existing conditions.

Why Other Options Are Wrong:
Option A: Violation concerns breaking or disregarding laws, which has no connection to a system that supports reforms. Option B: Impairing means making something worse, the opposite of improvement. Option C: Preservation refers to protecting something from change, so it conflicts with the idea of progress through reforms.

Common Pitfalls:
Some students may confuse reformism with revolution or may not distinguish between preserving traditions and reforming them. Another pitfall is to choose preservation because it seems like a formal noun, but its meaning does not match the phrase given. Always break down the descriptive phrase into core ideas and then map those ideas to the nearest technical term or abstract noun.

Final Answer:
The best one word substitute is Reformism, so option D is correct.