Which of the following is an example of rigid pipe?

Concrete pipe is considered an example of rigid pipe due to its structural properties. Rigid pipes are designed to handle loads from the surrounding soil and traffic without deforming. Their strength and durability make them suitable for underground applications where they might encounter significant external pressures.

Concrete pipe maintains its shape under these conditions, ensuring effective flow and minimizing the likelihood of leaks or structural failure. This characteristic is key in collection systems, where the integrity and reliability of the pipeline are critical for successful operation. Other materials, like ductile iron and steel, while strong, exhibit more flexibility under certain conditions compared to concrete, and thermoplastic pipes are noted for their flexibility, which differentiates them from rigid systems.