In the following idiom and phrase question from current affairs and politics, select the option that best explains the expression "ethnic cleansing".

Introduction / Context:
The term "ethnic cleansing" is a serious expression widely used in discussions of human rights, war crimes, and international politics. It refers to violent actions taken against a particular ethnic group in order to remove them from a region. Understanding this term correctly is important because it appears often in news reports, history texts, and examinations that deal with global issues.

Given Data / Assumptions:

• The phrase is "ethnic cleansing".
• The context is political or military, not hygiene or culture in a casual sense.
• Options describe different types of social change or violence.
• We need the option closest to the mainstream understanding used in international law and media.

Concept / Approach:
"Ethnic cleansing" refers to systematic, often violent actions aimed at removing a particular ethnic group from a territory. This can involve mass killing, forced displacement, intimidation, and other atrocities. In many cases, it includes large scale killing of members of the targeted group and is closely related to genocide. Among the given options, the one that emphasises "mass killing of members of one ethnic group" captures the central and most horrific aspect of the term as used in common discourse and exam contexts.

Step-by-Step Solution:
Step 1: Focus on the word "ethnic", which refers to groups defined by shared culture, language, or ancestry. Step 2: Focus on "cleansing", which is used metaphorically to indicate removal, not literal cleaning. Step 3: Combine these ideas: violent removal of an ethnic group from an area. Step 4: Compare the options and find the one that directly mentions "mass killing of members of one ethnic group". Step 5: Confirm that this option matches how the phrase is reported in serious international news and human rights discussions.

Verification / Alternative check:
We can verify by recalling events in recent history where the term "ethnic cleansing" has been used, such as conflicts in the Balkans, Rwanda, or other regions. Reports describe targeted killing, forced displacement, and destruction aimed specifically at one ethnic community. While the full concept may include expulsion and terror, mass killing is a key feature and is therefore fairly represented by the correct option given in this question.

Why Other Options Are Wrong:
Option a: "a social revolution where negative aspects of a culture are removed" describes cultural reform, not violent targeting of an ethnic group. Option b: "to perform mass religious conversions" deals with religion, not necessarily with ethnicity, and does not inherently involve killing or expulsion. Option d: "removal of all signs of culture from a society" suggests cultural erasure in general, not the targeted abuse of a specific ethnic group.

Common Pitfalls:
Some students may be misled by the word "cleansing" and suppose it refers to some kind of cultural or moral purification without realising the extreme violent reality behind the term. It is important to understand that in modern political vocabulary, "ethnic cleansing" is a euphemism for actions that are often criminal and inhumane, including mass killings. Recognising this helps you interpret news and exam questions more accurately.

Final Answer:
The expression "ethnic cleansing" refers to the mass killing of members of one ethnic group, usually as part of a campaign to drive them out of a region.