Statements: • All pens are clocks. • Some clocks are tyres. • Some tyres are wheels. • Some wheels are buses. Conclusions: I. Some buses are tyres. II. Some wheels are clocks. III. Some wheels are pens. IV. Some buses are clocks. Choose the option that must follow.

Introduction / Context:
This is a chain of three “some” statements with a single unrelated universal. Without a universal link across those “some” statements, no intersection among the endpoints is forced.

Given Data / Assumptions:
∃c_t ∈ Clocks ∩ Tyres; ∃t_w ∈ Tyres ∩ Wheels; ∃w_b ∈ Wheels ∩ Buses; Pens ⊆ Clocks. The witnesses can all be different.

Concept / Approach:
I needs the Wheel-Bus and Tyre-Wheel witnesses to coincide; not forced. II needs the Tyre-Clock to also be a Wheel; not forced. III then needs that Wheel to be a Pen; not forced. IV needs a Wheel-Bus that is also a Clock; not forced.

Step-by-Step Solution:
• Construct a model with three distinct witnesses c_t, t_w, w_b. All premises hold; I–IV are all false.• Because truth values can vary across permitted models, none of the conclusions is necessary.

Verification / Alternative check:
Even though Pens ⊆ Clocks, there is no statement connecting Pens to Tyres or Wheels.

Why Other Options Are Wrong:
They overstate what “some” statements can guarantee.

Common Pitfalls:
Assuming transitivity for “some” across multiple steps.

Final Answer:
None follows.