ANS:C - safety of welder is ensured.

The statement "safety of welder is ensured" is not accurate in the context of why friction lighters are used for lighting gas welding torches. Friction lighters are primarily chosen for their ability to produce a quick and intense spark, which efficiently ignites the gas used in welding torches. While ensuring the safety of the welder is an important consideration in welding operations, it is not directly related to the use of friction lighters. Instead, safety measures in welding typically involve proper training, use of personal protective equipment (such as welding helmets, gloves, and protective clothing), proper ventilation to remove fumes, and adherence to safety protocols to prevent accidents and injuries during welding operations.