Which of the following scenarios might lead to a potential safety hazard when using gas piping?

Using gas piping as an electrical ground creates a potential safety hazard primarily because gas piping systems are designed exclusively for carrying gas and not for conducting electricity. If gas piping is inadvertently used as a ground, it could lead to a dangerous scenario where electrical faults might result in sparks or arcing, that could ignite any gas leaks present, leading to explosions or fires.

In contrast, while the other scenarios may also have their own safety considerations, they do not present the same level of immediate danger. Gas piping exposed to sunlight can degrade materials over time but does not pose an instant hazard like using gas piping for electrical grounding. Running gas piping parallel to water pipes does not inherently create a hazard, although proper installation practices should be followed to prevent corrosion or condensation issues. Flexible gas connectors are typically safe when properly installed, allowing for movement and reducing stress on rigid piping because they are designed specifically for gas applications.