Correct option is D
The ratio of oxygen to acetylene in a neutral flame is 1:1. A neutral flame is achieved when equal volumes of oxygen and acetylene are mixed, resulting in a balanced combustion that neither oxidizes nor carburizes the material being welded. This type of flame is most commonly used in oxy-acetylene welding for general-purpose applications, as it produces a clean and controlled heat suitable for welding a wide range of metals.
