Answer : Option D

Explanation :

Flames are formed when a fuel gas, like acetylene, reacts with a support gas such as oxygen. This reaction creates a lot of heat and light, which we see as a flame. An oxygen acetylene flame can create temperatures over 3200°C. Pure oxygen, instead of air (20% oxygen/80% nitrogen), is used to increase the flame temperature to allow localized melting of the work piece material (e.g. steel) in a room environment. A common propane/air flame burns at about 3,630 degree F (2,000 degree C), a propane/ oxygen flame burns at about 4,530 degree F (2,500 degree C), and an acetylene/oxygen flame burns at about 6,330 degree F (3,500 degree C).