Brick kilns — identify the correct statements about common kiln types. Choose the best combined option.

Introduction / Context:
Different brick kiln designs influence fuel efficiency, product uniformity, and capital cost. Recognizing the physical form and operating principle of standard kiln types is fundamental in building materials and construction management. This question checks whether you can match descriptive statements to Bull's trench kilns, Hoffman's kilns, and tunnel kilns.

Given Data / Assumptions:

• Bull's trench kiln (BTK) is usually an excavated oval/rectangular trench.
• Hoffman's kiln is a permanent, above-ground annular kiln with chambers.
• Tunnel kiln is a long, refractory-lined tunnel with moving cars.

Concept / Approach:
BTK is a continuous kiln where a fire moves along an in-ground trench; Hoffman's kiln is a classic overground, chambered continuous kiln; tunnel kilns are modern continuous systems where ware travels through distinct preheat, fire, and cooling zones. Each statement provided is a direct description of the kiln's construction style or operating concept.

Step-by-Step Solution:

Verification / Alternative check:
Standard building materials texts and brick industry descriptions confirm these definitions and construction forms.

Why Other Options Are Wrong:
Any single-statement option omits the correctness of the remaining true statements; only the aggregate option captures all truths.

Common Pitfalls:
Confusing BTK (in-ground) with clamp burning; mixing up continuous vs intermittent operation across kiln types.

Final Answer:
All of the above