Which items are included in the components of manholes?

The correct answer includes components that are essential parts of manholes, specifically focused on their structural and functional elements.

Manholes typically consist of bases, covers, and risers, which are integral to their design and purpose in sewer systems. The base is the bottom part that provides a foundation, the risers extend the height of the manhole, and the cover ensures that the opening is sealed when not in use. This combination ensures that the manhole can accommodate changes in depth and provides access for maintenance while protecting against contaminants.

While other choices include items relevant to plumbing and drainage systems, they do not exclusively relate to the direct components of manholes. For instance, frames, grates, and ladders are used in various drainage applications but are not standard terms specifically defining manhole construction. Barrels, lids, and cones generally refer to different types of structures and do not capture the essential elements found in manholes.

By recognizing the correct components, you can better understand how manholes function within a collection system and the role each part plays in ensuring effective access and maintenance of underground utilities.