In this idiom and phrase question, choose the option that best expresses the meaning of the expression "a bone of contention".

Introduction / Context:
Idiom questions assess your understanding of fixed expressions that carry meanings beyond the literal meanings of their individual words. The phrase a bone of contention is a traditional English idiom often used in discussions about disputes, negotiations, and conflicts. To answer correctly, you need to know what the whole expression refers to in real life situations rather than trying to interpret it word by word.

Given Data / Assumptions:

• The idiom given is a bone of contention.
• The options describe different possible interpretations involving agreement, property, and happiness.
• The expression appears in contexts involving disagreement or argument.
• We must find the option that matches the idiomatic meaning used in general English.

Concept / Approach:
In literal terms, a bone can be something that animals fight over. Figuratively, a bone of contention is an issue or subject that people argue about repeatedly and cannot resolve easily. It is the central point of dispute. Therefore, the meaning focuses on continuing disagreement rather than agreement or property. Recognising the metaphor helps you connect the idiom to the correct explanation among the options.

Step-by-Step Solution:
Step 1: Recall the idiomatic meaning you may have seen in news or literature, where a bone of contention refers to a controversial issue.Step 2: Read each option and see which one matches the idea of an issue people keep arguing about.Step 3: Option B says an issue over which there is continuing disagreement, which aligns exactly with this idea.Step 4: Option A talks about the only part on which two arguing parties agree, which is the opposite of contention.Step 5: Option C suggests a very expensive inherited property, which relates to wealth, not the concept of argument itself.Step 6: Option D refers to being happy with only a few things, which describes contentment, not contention.

Verification / Alternative Check:
Consider sentences such as The boundary line has long been a bone of contention between the two neighbours or The distribution of resources is a major bone of contention in the negotiations. In these examples, the phrase clearly refers to the main disputed issue. Replacing the idiom with an issue over which there is continuing disagreement keeps the meaning intact. None of the other explanations fits these sentences, which verifies that option B is correct.

Why Other Options Are Wrong:
Option A describes agreement, which contradicts the word contention that signals dispute or conflict. Option C introduces the idea of inheritance and cost, which may sometimes cause disputes but is not built into the idiom itself. Option D confuses contention with contentment, which are opposite ideas in English. Contentment refers to satisfaction and peace, while contention refers to conflict and disagreement. Therefore these choices do not represent the idiom accurately.

Common Pitfalls:
One common trap is misreading contention as contentment and therefore choosing an option related to happiness. Another mistake is to focus too literally on bone and imagine property or physical objects instead of understanding the phrase as a metaphor for a disputed matter. To master idioms, it is helpful to learn them as complete units with example sentences rather than trying to decode them word by word during the exam.

Final Answer:
The idiom a bone of contention means: an issue over which there is continuing disagreement.