In the following question on English idioms, choose the alternative which best expresses the meaning of the expression Bad blood, used to describe negative feelings between people or groups.

Introduction / Context:
This idiom question tests your understanding of the phrase Bad blood. The expression is often used in news articles, biographies, and social discussions to describe long lasting negative feelings between individuals, families, or communities. It does not refer to the medical condition of blood, but to emotional hostility or resentment.

Given Data / Assumptions:

• Idiom: Bad blood.
• Options include war, ill feeling, threatening attitude, and an infected state.
• The task is to choose the alternative that best matches the figurative meaning.
• The context is social or emotional relationships rather than physical health.

Concept / Approach:
Bad blood refers to ongoing hostility, resentment, or ill will between parties, often based on past conflicts or perceived wrongs. It may not show as open fighting, but the relationship is damaged and unfriendly. The correct answer must convey this sense of negative emotion. While war and threatening attitude describe open conflict or aggression, ill feeling accurately captures the emotional background that the idiom emphasises. The option about infected state confuses the metaphor with literal medical language and is not correct.

Step-by-Step Solution:
Step 1: Recall that bad blood is used when people talk about old quarrels or grudges that still affect relationships. Step 2: Examine option a, war, which means active armed conflict and is much stronger than the emotional state implied by the idiom. Step 3: Examine option b, ill feeling, which suggests resentment, dislike, or hostility held in the mind. Step 4: Examine option c, threatening attitude, which refers to a visible posture of threat, not necessarily long term resentment. Step 5: Examine option d, in an infected state of being, which misreads blood literally and refers to physical sickness. Step 6: Conclude that ill feeling is the closest match to the idiomatic meaning.

Verification / Alternative check:
Imagine the sentence There has been bad blood between the two families for years. If we replace bad blood with ill feeling, the sentence becomes There has been ill feeling between the two families for years, which keeps the meaning intact. Replacing it with war would imply ongoing armed conflict, which is not always the case, and in an infected state of being would sound medically incorrect. This confirms that ill feeling is the best option.

Why Other Options Are Wrong:
War: Indicates open armed conflict rather than the underlying emotional hostility described by the idiom.
Threatening attitude: Focuses on visible behaviour at a particular time, not on long term resentment.
In an infected state of being: Takes the metaphor literally and refers to physical disease, which is not the idiomatic sense.

Common Pitfalls:
Some candidates are misled by the medical association of blood and choose options related to infection. Others overstate the level of conflict and choose war. To avoid such errors, remember that idiomatic phrases like bad blood and bad taste in the mouth often describe emotional reactions, not medical conditions. When you see bad blood in reading passages, pay attention to whether the passage mentions past quarrels, jealousy, or longstanding grudges. That context will reinforce the meaning of ill feeling in your mind.

Final Answer:
The idiom Bad blood refers to ill feeling, so option b is correct.