Syllogism — Doors, Buses, Leaves, Flowers Statements: • All doors are buses. • All buses are leaves. • No leaf is a flower. Conclusions: I. No flower is a door. II. No flower is a bus. III. Some leaves are doors. IV. Some leaves are buses.

Introduction / Context:
This question uses two universal inclusions and one universal exclusion. The task is to infer which universal negatives are forced and whether any particular (“some”) statements can be deduced without explicit existence information.

Given Data / Assumptions:

• Doors ⊆ Buses ⊆ Leaves.
• Leaves ∩ Flowers = ∅.

Concept / Approach:
When a class is a subset of a class disjoint from another, it is also disjoint from that other class. However, “All A are B” does not by itself guarantee existence of A or B, so you cannot conclude “Some B are A” unless a “some” premise provides existence.

Step-by-Step Solution:

Verification / Alternative check:
Build a model with empty Doors/Buses classes; the universal statements remain true, yet III and IV would be false, proving they are not logically necessary.

Why Other Options Are Wrong:

• Options listing III or IV assume existence not given by the premises.
• “All follow” overstates; only the two universal negatives are compelled.

Common Pitfalls:
Committing the existential fallacy—deriving a particular conclusion (“some …”) from only universal premises.

Final Answer:
Only I and II follow