Syllogism — Books, trees, and lions (existential note): Statements: (1) All books are trees. (2) All trees are lions. Conclusions: I. All books are lions. II. All lions are books. III. All trees are books. IV. Some lions are books.

Introduction / Context:
We examine inclusion chaining and the careful use of existential import for particular conclusions.

Given Data / Assumptions:

• Book ⊆ Tree.
• Tree ⊆ Lion.

Concept / Approach:
From chaining, Book ⊆ Lion, so I holds. II and III reverse inclusions and are not compelled. IV “Some lions are books” follows under the standard test assumption that the subject classes are non-empty (i.e., books exist). This is commonly assumed in competitive-exam syllogisms when particulars are drawn from universals.

Step-by-Step:
1) Compose inclusions to derive Book ⊆ Lion.2) I follows immediately.3) II and III are unsupported reversals.4) If at least one Book exists (standard assumption), that entity is a Lion; hence IV holds.

Verification:
Let one book exist; then at least one lion is a book (the same entity), validating IV.

Final Answer:
Only I and IV follow.