Identify a common maintenance task for gas appliances.

Regularly checking and cleaning the burners is crucial for maintaining gas appliances because it ensures they operate efficiently and safely. Over time, burners can accumulate dirt, grease, and food particles, which can obstruct gas flow and lead to incomplete combustion. This can not only reduce the appliance's efficiency, leading to higher gas bills, but it can also pose safety risks, such as gas leaks or the production of harmful carbon monoxide. Routine maintenance like this helps in identifying issues early, ensuring that the appliance functions safely and effectively.

The other options, while related to maintenance, do not reflect common practices for everyday upkeep. Replacing gas lines every year is excessive and not typically necessary unless there are signs of wear or damage. Upgrading to the latest model is a decision that might arise after years of usage and not a routine maintenance task. Painting the appliance surface is more of a cosmetic task than a necessary maintenance step, as it does not affect the appliance's functionality or safety.