What is the most common application for compression fittings with copper tubing?

The most common application for compression fittings with copper tubing is connecting refrigeration components. In refrigeration systems, various components such as compressors, evaporators, and condensers need to be interconnected. Compression fittings are particularly valued in these applications because they create a strong, leak-proof seal without the need for soldering, making installation and repairs easier and quicker.

This method is especially advantageous for refrigeration systems where frequent maintenance might be necessary. The ability to disconnect and reconnect without damaging the tubing is crucial in ensuring system efficiency and reducing downtime. Compression fittings also allow for the secure attachment of different components while accommodating slight misalignments that can occur during installation.

While sealing high-pressure lines, crossover connections, and liquefying refrigerants are important aspects of refrigeration systems, they do not primarily involve the use of compression fittings in the same way that connecting refrigeration components does. Therefore, the focus on connecting various parts makes option B the correct choice.