Statements: • All chairs are tables. • All tables are desks. • Some desks are benches. • Some desks are sofas. Conclusions: I. Some benches are sofas. II. Some sofas are tables. III. Some benches are tables. IV. No chair is a bench. Choose the option that must follow.

Introduction / Context:
The problem combines two universal inclusions with two separate existential statements about the same super-set. We must avoid assuming that the two “some” subsets coincide unless that is stated.

Given Data / Assumptions:

• Chairs ⊆ Tables ⊆ Desks.
• Some Desks are Benches.
• Some Desks are Sofas.

Concept / Approach:
Conclusions about overlap between Benches and Sofas (I) or their overlap with Tables (II, III) require that the particular desks which are benches are the same as the desks which are sofas or tables in a way that creates the claimed intersections. The premises do not guarantee any such coincidences. Universal statements alone do not produce existence claims for Chairs or Tables either.

Step-by-Step Solution:
• I: “Some benches are sofas” needs benches ∩ sofas ≠ ∅. The premises permit benches and sofas to be disjoint subsets of Desks.• II and III: To get “some X are tables,” we would need elements shown to be tables. Existence of tables is not provided by “All chairs are tables” unless chairs exist, which is not given. Also, benches/sofas need not intersect tables.• IV: “No chair is a bench” is not implied; Chairs could be disjoint from or overlap Benches within Desks, since nothing forbids it.

Verification / Alternative check:
Model Desks = {b1 (bench), s1 (sofa)} with Tables = Chairs = ∅. All premises hold, and none of the conclusions follows.

Why Other Options Are Wrong:
They all assume overlaps that are not forced by the premises.

Common Pitfalls:
Reading “some” lines as if they referenced the same individuals.

Final Answer:
None follows.