Final answer:
Gas piping can be constructed from a variety of materials, including steel, copper, brass, and plastic polymers, each chosen based on specific application requirements and safety standards.
Step-by-step explanation:
The material gas piping or tubing can be constructed of is d) A variety of approved materials. Gas pipelines can be made from several different materials, depending on the specific requirements and applications. Common materials include steel, which is often used due to its strength and durability. Copper, known for its good thermal conductivity and flexibility, is another option, often seen in residential gas installations. Brass fittings may also be used in conjunction with copper piping for gas. Furthermore, various types of plastic polymers, such as polyethylene, are used for gas pipes, particularly for low-pressure or distribution systems. Each material comes with its own set of advantages and regulatory considerations, and must meet safety standards in order to be used for gas piping.