The correct answer is: B. Manhole
A manhole is a cylindrical structure that provides access to a sewer line. It is typically made of concrete or steel and has a diameter of about 4 feet. Manholes are typically located at regular intervals along a sewer line, and they allow workers to inspect and clean the line.
An inlet is a structure that allows water to flow into a sewer line. It is typically made of concrete or steel and has a grate or screen to prevent large objects from entering the line. Inlets are typically located at the bottom of storm drains or gutters.
A drop manhole is a type of manhole that is located at a point where the sewer line changes direction or elevation. Drop manholes are typically larger than regular manholes and have a ladder or stairs to allow workers to access the lower level of the sewer line.
A catch basin is a small structure that is located at the bottom of a storm drain or gutter. It is typically made of concrete or steel and has a grate or screen to prevent large objects from entering the sewer line. Catch basins also collect sediment and debris, which can be removed periodically to prevent clogging of the sewer line.