Difficulty: Medium
Correct Answer: Conclusion II follows
Explanation:
Introduction / Context:
This question deals with logical relations among three sets that correspond to animals: crows, jackals, and foxes. You must interpret the sets abstractly and ignore real world biology. The statements describe overlap between crows and jackals and a complete separation between crows and foxes. You then judge whether the conclusions about jackals and foxes follow from this information.
Given Data / Assumptions:
- Statement I: Some crows are jackals, meaning the intersection between the sets of crows and jackals is non empty.
- Statement II: No fox is a crow, meaning the sets foxes and crows are completely disjoint.
- Conclusion I: Some jackals are foxes, which asserts that the jackal set and fox set have a non empty intersection.
- Conclusion II: Some jackals are not foxes, which asserts that at least one jackal lies outside the fox set.
Concept / Approach:
Use set notation: let C be the set of crows, J the set of jackals, and F the set of foxes. From Statement I, C ∩ J is non empty. From Statement II, F ∩ C is empty. We are asked about the relation between J and F. Notice that there is at least one element that is both a crow and a jackal, and that no element of C can be in F. This will help us decide whether there must exist jackals that are not foxes.
Step-by-Step Solution:
Step 1: Because some crows are jackals, there exists an element x such that x ∈ C and x ∈ J.
Step 2: Because no fox is a crow, no element of C can also belong to F. Symbolically, C ∩ F is empty.
Step 3: Since x is in C, x cannot be in F. Therefore, x is a jackal that is not a fox.
Step 4: This directly proves that at least one jackal is not a fox, which means Conclusion II must be true.
Step 5: Now check Conclusion I, which says some jackals are foxes. We have no information that connects J directly to F other than the indirect connection through C, and that connection only tells us that some jackals are crows, not that any jackals are foxes.
Step 6: It is possible to draw a Venn diagram where J and F have no overlap at all, while still satisfying both statements. In that case, Conclusion I would be false.
Step 7: Therefore, Conclusion I does not logically follow, while Conclusion II is necessarily true.
Verification / Alternative check:
Draw C and J so that they overlap in some region, representing crows that are jackals. Then draw F as a separate set that does not touch C at all, as required by Statement II. Because the overlapping region C ∩ J is prohibited from lying in F, there is at least one jackal in that overlap which cannot be a fox. Thus the existence of a jackal that is not a fox is guaranteed in every diagram, confirming Conclusion II. At the same time, you can place F completely away from J, showing that some jackals are foxes is not forced by the statements.
Why Other Options Are Wrong:
Option A picks Conclusion I, which is not supported. Option C suggests that exactly one of I or II follows but leaves ambiguity; however, the question requires a specific choice. Option D claims both conclusions follow, which cannot be because one conclusion is optional while the other is necessary. Option E says neither follows, which is wrong because Conclusion II definitely follows from the given information.
Common Pitfalls:
Some test takers think that if some crows are jackals and no fox is a crow, they lack enough information and might conclude nothing follows. In fact, the overlap between crows and jackals combined with the separation of crows and foxes gives a guaranteed example of a jackal that is not a fox. Another pitfall is to assume that some jackals are foxes based on loose real world associations, which is not allowed in pure logic problems.
Final Answer:
The correct option is Conclusion II follows, because there must exist at least one jackal that is not a fox, while there is no logical requirement that any jackal has to be a fox.
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