Which option is used to connect pipes of the same diameter, creating a straight run of pipe?

The correct choice is couplings, which are specifically designed to connect two pipes of the same diameter, allowing for a straight, uninterrupted run of pipe. Couplings can be made from various materials, including metal and plastic, and are essential for maintaining the continuity of the pipe system. They facilitate easy assembly and disassembly during installation or repairs, making them a common choice in both refrigeration and plumbing applications.

Bushings are used to connect pipes of different diameters, fitting into a larger pipe to allow a smaller pipe to connect, which is not applicable in this case. Elbows are designed to change the direction of piping, creating corners or turns, rather than providing a straight connection. Nipples, which are short pieces of pipe with threads on both ends, are often used to connect fittings but are not as versatile as couplings for creating a seamless pipe run. Thus, couplings are the suitable option for connecting pipes of the same size in a straight line.