In the following question below are given some statements followed by some conclusions based on those statements Taking the given statements to be true even if they seem to be at variance from commonly known facts. Read all the conclusions and then decide which of the given conclusion logically follows the given statements.

Statements:

I. All Z are Y.

II. Some Y are B.

Conclusion:

I. Some B are not Z.

II. Some Y are not Z.

III. Some Z are Y. 

Given Statements:

I. All Z are Y.

II. Some Y are B.

The least possible Venn diagram for the given statement is:

Conclusions:

Conclusion I: False ("Some B are not Z" is not true because there is no negative relation between B and Z. It may be possible but not definitely true. In syllogism, we take the definite cases as true. So this conclusion not follow.)

Conclusion II: False ("Some Y are not Z" is not true because there is no negative relation between Y and Z. It may be possible but not definitely true. So, this conclusion also not follow.)

Conclusion III: True ("Some Z are Y" is true because when all Z are Y is given then "some Z are Y" is also true. Please note that "some" is a subset of "all". For example, when all boys are male, then "some boys are male" is also true.) 

So, Only conclusion III follows.

Hence, the correct answer is "Option 3".

Mistake PointsNegative Conclusions will never be definitely true when a given statement is positive.
Here, Conclusion I & II is negative, so it will be true in possibility only.