Each of the following options presents a small argument with premises and a conclusion. Three arguments are logically correct if you ignore factual absurdity. One argument is logically wrong or doubtful. Which argument is logically incorrect?

Introduction / Context:
This question again tests your understanding of logical validity in syllogisms. You are asked to identify which argument is logically wrong or doubtful when you focus only on the structure of the reasoning and not on whether the premises sound realistic. Some arguments may have absurd sounding premises but still be valid, while another has a faulty generalisation that does not follow from the given information.

Given Data / Assumptions:

• We must treat premises as temporarily true and judge whether the conclusion necessarily follows if the premises hold.
• We ignore real world knowledge about houses, trees or physical laws and rely on pure logical form.
• In each option, two or more sentences lead to a conclusion about a broader group or category.
• Exactly one argument fails to be logically valid; our task is to find that argument.

Concept / Approach:
An argument is valid if there is no possible situation in which all premises are true but the conclusion is false. If such a situation exists, the argument is invalid or doubtful. In these options we often move from statements about specific individuals or subsets to broader general statements. A classic error is hasty generalisation: assuming that what is true for one example is true for all members of a group. We check each option for such errors.

Step-by-Step Solution:
Option A: “Ramesh is tall. Ramesh is a boy. Therefore, boys are tall.” Here the premises only tell us about Ramesh. The conclusion talks about all boys. There could be many boys who are not tall. So it is quite possible for the premises to be true and the conclusion false. This is an invalid argument. Option B: “All who can fly are animals. Some birds can fly. Therefore, some birds are animals.” If all flyers are animals and some birds are flyers, then those particular birds are both birds and animals. So it must be true that some birds are animals. This argument is valid. Option C: “Men live in houses. Houses grow on trees. Trees float in water. Therefore, men float in water.” Although factually absurd, the logic is: All men live in houses; all houses are on trees; all trees float. If each link is treated as true, then everything that is a man belongs to the class that floats in water. The conclusion that men float in water logically follows. Option D: “All living things are mobile. Some non-living things are mobile. Therefore, some mobile things are living and some are non-living.” If every living thing is mobile, then living things form a subset of mobile things. If some non-living things are mobile, then mobile things include at least one living and at least one non-living example. Hence the conclusion correctly summarises the situation and is valid.

Verification / Alternative check:
To verify option A is invalid, imagine a world with two boys: Ramesh and Suresh. Let Ramesh be tall and Suresh be short. Both premises “Ramesh is tall” and “Ramesh is a boy” are true. Yet the conclusion “boys are tall” is false because Suresh is not tall. This shows that the premises do not guarantee the conclusion. For options B, C and D, any interpretation that satisfies all premises will also satisfy the conclusion, which means those arguments are logically valid despite any factual absurdity in their content.

Why Other Options Are Wrong:
Options B, C and D are not wrong in the logical sense. In B, some birds inherit the property of being animals through flying. In C, men inherit the property of floating in water via the chain of houses and trees. In D, the set of mobile things contains examples from both living and non-living categories. Each of these conclusions faithfully reflects what must be true if the premises are taken as true.

Common Pitfalls:
Many test takers are distracted by the obvious factual nonsense in option C and conclude that it must be the incorrect argument. However, the instructions clearly tell you to ignore factual absurdity and concentrate on logical connections. Another common mistake is not noticing that option A tries to generalise from a single individual to an entire class without sufficient information. In logic questions, always ask whether the conclusion talks about more instances than the premises actually cover.

Final Answer:
The only logically wrong or doubtful argument is “Ramesh is tall. Ramesh is a boy. Therefore, boys are tall.”, which is option A.