Which of the following is a classification of cast iron pipe?

The classification of cast iron pipe is identified by the term "XH," which stands for "extra heavy." This designation indicates that the pipe has a greater wall thickness compared to standard or regular heavy cast iron pipes. The classification system for cast iron pipes is based on the pipe's ability to withstand pressure and its intended use, and the "XH" classification is important in specifying pipes for applications that require higher strength and durability.

In contrast, terms like Schedule 40 and Schedule 80 relate specifically to PVC and metal pipes, categorizing them based on their wall thickness and pressure ratings. These schedules are not applicable to cast iron pipes. "XS" stands for "extra strong," which is another classification used primarily for certain types of metals, but again, it does not specifically pertain to cast iron. Identifying "XH" as the correct classification helps ensure proper selection for plumbing applications that demand high performance and durability.