One word substitution: choose the word that can be substituted for the given description. The killing of a race or a large group of people of the same nation or ethnicity.

Introduction / Context:
This one word substitution question focuses on a serious historical and political term. It tests whether you can recognise the correct word for the deliberate killing of a race or a large group sharing the same nationality or ethnicity.

Given Data / Assumptions:

• Description: The killing of a race or a large group of people of the same nation or ethnicity.
• Options: Homicide, Genocide, Suicide, Murder.
• The correct word must refer to killing many people because of their group identity, not just individuals.

Concept / Approach:
Genocide is the term used for the deliberate and systematic destruction of a racial, political, or cultural group. The prefix geno refers to race or kind, and cide means killing. Homicide is killing a person, murder is the unlawful killing of a person with intent, and suicide is killing oneself. Only genocide covers killing of an entire race or group.

Step-by-Step Solution:
Step 1: Focus on the key phrase killing of a race. Step 2: Recall that cide means killing and that geno is linked to race or tribe. Step 3: Match this with Genocide, meaning killing of a race or ethnic group. Step 4: Reject other options which refer to killing individuals or oneself.

Verification / Alternative check:
History textbooks and news articles use genocide to describe events where entire communities are targeted because of their identity. No other term among the options is applied to such large scale, targeted killing. This confirms that genocide is the only correct answer.

Why Other Options Are Wrong:

• Homicide: Killing of a human being by another human being, usually at the level of individuals.
• Suicide: Act of intentionally killing oneself.
• Murder: Unlawful killing of a person with malice or intent, normally used for individuals or small numbers.

Common Pitfalls:
Students sometimes select homicide or murder simply because they see the idea of killing. However the description clearly mentions a race, which requires the more specific term genocide. Remember that examiners often test such fine distinctions to check precision in vocabulary.

Final Answer:
Correct option: Genocide.