Step 1: Understanding Syllogism.
In logic, a syllogism is a form of reasoning where two premises lead to a conclusion. If both premises are universal propositions (e.g., "All A are B"), the conclusion must also be a universal proposition. This is a fundamental rule in formal logic.
Step 2: Analyzing the Options.
- 1. Maybe universal or maybe particular: This is incorrect because a valid syllogism with universal premises leads to a universal conclusion.
- 2. Only Particular proposition: This is incorrect. A particular conclusion cannot follow from two universal premises.
- 3. Neither Universal nor Particular proposition: This is incorrect because the conclusion in a valid syllogism must be a universal proposition.
- 4. Only universal proposition: This is correct. If both premises are universal, the conclusion must also be universal.
Step 3: Conclusion.
The correct answer is 4. Only universal proposition.
Final Answer:
\[
\boxed{\text{The correct answer is 4. Only universal proposition.}}
\]