Geometry

Question Analysis:
This question involves recognizing a valid logical structure in geometry-based syllogisms.
The main focus is on identifying logically sound deductive reasoning.

Key Concept Explanation:
A syllogism is a form of logical reasoning that uses two premises to reach a conclusion.
A valid syllogism follows the form:
Major Premise: A → B
Minor Premise: B → C
Conclusion: A → C

Step-by-Step Solution:
Option A follows valid reasoning: "All squares are rectangles" (A → B), "All rectangles have four sides" (B → C), therefore "All squares have four sides" (A → C).
Option B is invalid because "All round things are blue" is an unfounded premise.
Option C is incorrect because some isosceles triangles are equilateral, but not all.
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